Big calculations, one stage at a time
Work out one quantity, then use it.
Mumbai and the buses
Estu wonders: “Could the entire population of Mumbai fit into 1 lakh buses?” Each bus holds 50 people. Mumbai had 1,24,42,373 people in 2011.
What do you think?
What this lesson covers
The idea
A large calculation is easier when it is carried out in stages, working out one intermediate quantity at a time and then using it in the next step.
Mumbai and the buses
Estu wonders: “Could the entire population of Mumbai fit into 1 lakh buses?” Each bus holds 50 people. Mumbai had 1,24,42,373 people in 2011.
What do you think?
- Yes, they fit
- No, they do not fit
- Cannot say without working it out
Work in stages
Solve each stage. The next one unlocks when you are right.
One stage at a time
A large calculation is easier in stages: work out one intermediate quantity at a time, then use it in the next step.
Stage 1: seats = 1 lakh × 50 = 50 lakh. Stage 2: compare 50 lakh with Mumbai’s 1 crore 24 lakh. Each stage is small, so nothing feels too big.
Notes
A large calculation is easier when it is carried out in stages, working out one intermediate quantity at a time and then using it in the next step.
Check yourself
Roxie can travel 100 km every day. How many days are there in 10 years? (Take 365 days in a year.)
Answer: 3650 days
365 × 10 = 3,650 days. This is stage 1.
Now stage 2. In 3,650 days at 100 km a day, how far does she travel?
Answer: 365000 km
3,650 × 100 = 3,65,000 km.
The Moon is 3,84,400 km away. Does Roxie reach it in 10 years?
- Yes, she passes it. 3,65,000 is less than 3,84,400, so she does not get there.
- Exactly on the Moon. 3,65,000 is not equal to 3,84,400.
- No, she is about 19,400 km short — correct. Yes! 3,84,400 − 3,65,000 = 19,400 km still to go.