Chapter 1

How many zeros are there in one lakh when written in digits?

If you eat 2 varieties of rice each day, how many varieties will you taste in 100 years (ignoring leap years)?

According to the 2011 Census, Chintamani had 75,000 people. How much less is this than one lakh?

The estimated population of Chintamani in 2024 is 106,000. How much more is this than one lakh?

Which floor count approximates Somu’s building height if Somu is 1 m tall and each floor is four times his height, given the building height is plotted up to 500 m?

Write 3,00,600 in words using the Indian system.

Convert ‘one lakh twenty three thousand four hundred and fifty six’ into digits (Indian system).

How many times press the +1000 button to reach 90,000 on the Thoughtful Thousands calculator?

On the Tedious Tens calculator, how many presses to show 780?

Find two different expressions to get 5072 using Creative Chitti’s buttons.

What is the smallest number of button presses to get 8300 on Systematic Sippy?

How many zeros are there in one crore when written in Indian format?

Read 4050678 in Indian place value notation and write its name in the American system.

Which estimate is closer for 463,128 + 419,682: near 800,000 or near 900,000?

Convert 14,63,128 – 4,90,020 exactly.

Which city’s population almost doubled between 2001 and 2011 in the given table?

What pattern is observed when multiplying 1111 × 1111?

Calculate 116 × 5 quickly using the shortcut shown.

Multiply 824 × 25 using division shortcut.

What is 1250 × 380? (fact about Purandaradāsa)

The average Amazon discharge per second is given by 6400 × 62,500. What is this product?

Could Mumbai’s population fit into 100,000 buses of 50 people each?

If you travel 100 km per day, how far in 10 years ignoring leap years?

Using 250 babies born per minute, will one million babies be born in a day?

Can you count one million coins in a day at one coin per second?

How many stick segments make the digit 7 in the toothpick activity?

Starting from 42,019 (23 sticks), adding two sticks yields 42,078. What is another valid bigger number?

Where to insert ‘1’ in 4 2 0 1 9 to get the largest number?

Using digits 0–9 once, what is the largest multiple of 5?

How many lakhs make a billion in Indian system?

What is the nearest lakh to 6,72,85,183?

Which American comma placement corresponds to Indian 1,00,00,000?

In the table of city populations, which city was ranked 5th in 2011?

Which large number name originates from Sanskrit lakṣha?

Write the seven nearest neighbours (thousand to crore) for 3,87,69,957: what is the nearest crore?

What is the name for 1,000,000 in the Indian system?

Estimate whether 4,63,128 + 4,19,682 is greater or less than 8,50,000.

What is the product of 101 × 101?

Which button combination gives the fewest presses for 20,800 on Systematic Sippy?

If a paper sheet weighs 5 g, can you lift 100,000 sheets at once?

How many days for a bar-tailed godwit to fly 13,560 km at approx. 1,200 km/day?

How many stick segments to write 5108 in toothpick digits?

What is the smallest five-digit number?