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Guesstimate 1 – Number of Office chairs sold in India

Q1. Estimate the number of office chairs sold in India.


To estimate the numbers of office chairs sold in India, we will proceed by estimating, working population in India.

Lets say, out of 120 crore population in India, 60% are people that are above the age of 15, i.e. equal to 72 crore.
Approximately 50% people are employed, which is equal to 36 crore of the working population in India.

Lets now assume 20% of the working population work from office where in we exclude the farmers, street vendors and drivers, etc).
Approximately 7.2 crore people in India work from office.

Thus, there are 7 crore people existing office chairs in India. Now we can either assume the time frame or ask the interviewer. 

If we assume, we can calculate the chairs sold in a year.

Hence, we can conclude that approximately 70 lakh office chairs are being sold in India.

Q2. How many total Gmail users are there in India?

Ans:  The population of India is – 1300000000.

       Internet penetration in India is – 30%

      Population Distribution –

  • 0-20 : 25%
  • 21- 60 : 60%
  • >60 : 15%

        people of age between 0-20 using internet = 0.25*390000000 = 97500000 =        100000000(aprrox.)

        Similarly people of age between 21-60 and >60 using internet will be 230000000 and 60000000 respectively.

People of age 0-20 usually do not need an email account. But we may consider 5% of them do have it. Therefore email users of 0-20 age group = 0.05*100000000 = 5000000.

The major proportion of email users are the employed people. Since in India employment rate is 75% but not all of them need an email account. We will assume 75% of employed people use an email account.

Therefore email users of age 20-60 = 0.75*0.75*230000000 = 130000000(approx.)

Out of 60000000 people aged above 60, 25% of them use an email account. So email users of this age group = 0.25* 60000000 = 15000000.

So total email users in India = 5000000 + 130000000 + 15000000 = 150000000.

Gmail is a free and most prominent email service provider. So the nearly 85% of email users use Gmail.

            Therefore number of Gmail users in India = 0.85*150000000 = 127500000.

3. Estimate how many items in a jar ?

Ans:  We will take a circular jar base, to use the simplest mathematics formula we will use the basic shape of a jar to calculate the number of candy pieces.

Also the jae will change its diameter.

Lets assume the diameter is 5 cm wide, hence, radius is 2.5 cm. The area of the base is r^2 times Pi. therefore, area = 2.5*2.5*3.14 = 19.63.

For volume, we will assume a cylinder and later add a few pieces.

We take area and multiply it with the height of the cylinder. Lets estimate this again, making the final results inaccurate as it all depends on how good we are at estimating.

Height of the candy is 7 cm, hence V = 7*19.63 = 137.4 cubic cm.

Lets use 0.8 as a value, as thats the normal size of a candy.

If we split the jar into four sides and count the candy pieces, there are about 25 extra pieces on each side. So we add 100 to the equation. Ans- 272 pieces.

4. How many paan shops are there in India ?

Ans: We will use the method of Demand and Supply

 Total population of India = 1.2bn or 1200 Mn

Male = 700 Mn & Female = 600 Mn ( 900 women per 1000 men )

The ratio of Female/Male for Pan consumption is very small.

Female in india those consume pan on regular basis = 2% = 600Mn*.01 -> 12Mn

Divide male on the basis of age groups :

0–15 ->  neglect this section

16–22 -> 15% of 700Mn = 105Mn -> 5Mn ( This is the college age & as per my own college scenario 5 students consume pan out of the 100)

23–50 -> 35%of 700Mn = 240 Mn -> 20% people consume -> .2*240 -> 48Mn

51–80 -> 20% of 700Mn=140Mn -> older age, various problems like in teeth -> .05*140

-> 7Mn

Total demand of pan = 12+5+48+7 = 72 Mn

Using Supply :

time taken to make 1 pan = 2min -> 30 in 1 hour

Lets pan shop opens for 10 hours -> 30*10 = 300 pan

Number of pan shops in india= 72 Mn/ 300 = 2,40,000 ~ 2.5 lakh

5. Estimate the total length of roads in your city

 Ans: If we take Mumbai and say Blue Dart, it will take 1 delivery truck for a region like Andheri from the regional distribution center.

Andheri is assumed as approximately 25km^2 in area.

a delivery truck driver would work for 7 hours a day driving, at a speed of 30–40 kmph (Andheri being congested).

So kilometers he clocks in a day: 30*7 = 210 km.

Now generally the delivery schedule is planned in a such a way that all deliveries happen in the most efficient way. (Operations Guys at the firm would be getting paid lakhs for ensuring this shit!, but then technology rules! )

So assuming up and down journey, I would assume length of the roadways in Andheri area as 210/2 = 105 km.

But provisioning for some scope of redundancy during the travel, I would take 70% uniqueness factor.

That gives us ~ 70km

Also some of the aeas would be covered by bike delivery guys: say 3o% of wat truck covers (as bikers cover short distances) = ~20km

Also 10–15 km for postman/walker delivery personnel : ~ 10km

So total road length for Andheri ~ 100km

Now, Mumbai city area: 600km^2

So Andheri like region = 600km^2 / 25 = 24

Assuming a coverage ratio of the courier service to be 90%

Regions covered: ~22

So total road length ~ 22*100 = 2200km.

6. How much is the surf excel detergent usage in a day in India?

Ans:   India has a population of approx 1.2B People.

About 20% are BPL and would therefore not use surf excel. Remaining population: o.8*1.2B = 0.96B people.

Assuming a family of 4 people that is 0.24B families.

Rural:Urban = 30:70 (0.072B:0.168B)

Assuming only about 10% of people use surf excel in ruler areas, due to the availability of other cheaper mediums that will be 16M Families.

Due to competition and availability of substitutes in urban areas, assuming surf excel has a market share of 40%, that will be about 28M families.

Total user base: 44M Families.

Everyday usage must be at least 10 grams, total usage = 440 Million gms of surf excel everyday.

7. How do we estimate the area of an Airport ?

Ans: Let’s assume the airport can accommodate 10 planes at once and handle 5 runways.

Average length of runway = 2000m

Width of runway = 50 m

The total area of runway is 2000*50*5 = 500000 sq.m

Length of average plane is assumed as 50m and its wingspan is 40 m.

Total area of 10 planes = 20000+500000 = 520000 sq.m

Now somes assumptions, total area occupied by the building is equal to the area of runways and planes i.e 520000 sq.m

Total area of airport = 104000 sq.m.

There is a lot of empty space on an airport so we assume 40% of the total hence the final area is = 104000/0.6 = 1700000 sq.m.

8. How to estimate the number of ambulances on the road ?

Ans: Let’s start with the population of the country ~ 1.3 Billion (1300 million)

Rural – 70% = 900 million Urban 400 million

Let’s divide the Urban population into three groups based on income level – Low |High |Upper High

I would divide as : Low: 30% High – 50% Upper High – 20%

So Urban Low: 120 million High – 200 Upper High – 80 million

Now out of Urban Low I would assume 10% have driving as occupation (Rise of taxi services etc. (only considering 4 wheeler drivers))

= 12 million (120,00,000)

Out of these I would assume 1–1.5% are ambulance drivers = 120000

So we can say almost 1,20,000 ambulances are available in the country at any time.

Now generally ambulances are available on calling, that means, at least a half of them are always on backup. let’s assume that 70% of them are on idle at any given point of time.

Also since their average journey time is of 20–25 minutes, so we can say not more than 10% of ambulances would be on road at any time

So we can say 10% are on roads at any time = 12000 ambulances on road across Urban India.

9. How many red colour Swift cars are there in Delhi ?

Ans:  Let’s start with the population of Delhi which is 2 Crores.

We will divide this population into two groups-

1. Family(80%) = 0.8*20000000 = 16000000 family members

2. Bachelors(Individuals) (20%) = 0.2*20000000 = 4000000

Number of families(assuming 4 members in each) = 16000000/4 = 4000000.

Guessing that 50% of families have cars, so the number of families with cars = 2000000.

In Delhi, we can assume that 25% of the families belong to high class society so they can afford 2 cars on an average and the rest can afford only one car.

Therefore number of cars with families = 0.25*2000000*2 + 0.75*2000000*1 = 2500000.

Now let’s say only 10% of the individual population can afford a single car.

Therefore, number of cars with individuals = 0.10*4000000 = 400000.

So the total number of cars in Delhi can be estimated as 2500000+400000 = 2900000 which can be rounded of to 3000000 for simple calculations.

Since Maruti being the Indian market leaders in car sector so we can safely assume 50% of cars on the roads of Delhi are of Maruti, i.e., 1500000 cars.

Swift is one of the most common and affordable models along with Alto, WagonR, Omni and 800. So let’s assume there are 200000 Swifts.

White, silver, grey, black are the most common colors. So 75%(approx) of Swifts will be of these colors.

Now we are left with 50000 Swifts of different colors. Considering red, yellow, blue, maroon and orange as possible other colors,we can guess that there are nearly 10000 red Swifts in Delhi.

10. Guess-estimate the number of people wearing watches in Bangalore.

Ans:      Let’s assume population of Bangalore as 10 million and the day today is a working day for every age group

And age group wise population assumption would be

0–15 yrs: 30%; 15–25 yrs: 20%; 25–50 yrs: 30%; >50 yrs: 20%

Income wise population would be

Above poverty line: 75%

The people below poverty has negligible chance to use a watch, so I am eliminating this 25% population from every age group.

Now we have 75% of aforesaid % in every age group. As below poverty is eliminated 0–15 group mostly have school children and infants I assume 5% of them wearing watches today. So the count would be 2.25 million*5%=112500

15–25 age group have majority of higher education students who spend most of their time using mobile phones, so people using watches may be nearly 25% which gives 1.5 million*25%= 375000

25–50 groups have professionals working somewhere for their survival whose generation recently entered the smartphone culture. So most of them use watches. If out of this group, if 90% are couples, we will approximately have 20% housewives in it. As there is less chance of housewives wearing watches we can neglect it. The remaining 80% population say 90% wear watches, then count would be (80%*2.25 million)*90%=1620000

Coming to >50 group say 25% are working somewhere having 90% of them wearing watches again and in remaining 75% let 20% wear watches as we see many of our grandfathers wearing watches even in house. So count would be (25%*1.5 million)*90%+(75%*1.5 million)*20%= 562500

Total= sum of all these=2.67 million wear watches

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