Math Quiz

A restaurant bill comes to ₹200 and you leave a 15% tip. How much is the tip?

• ₹15
• ₹30
• ₹20
• ₹35

Answer: ₹30. 15% of 200 = 15/100 x 200 = 30. Quick trick: 10% is ₹20, 5% is half of that (₹10), so 15% is ₹30.

How many zeros are there in one crore when you write it in digits?

• 5
• 6
• 8
• 7

Answer: 7. One crore is 1,00,00,000, which has 7 zeros. In the international system it is 10 million.

A train covers 180 km in 3 hours at a steady pace. What is its speed?

• 60 km/h
• 90 km/h
• 540 km/h
• 45 km/h

Answer: 60 km/h. Speed = distance ÷ time = 180 ÷ 3 = 60 km/h. 540 is what you get if you multiply instead of divide.

What comes next in this pattern: 1, 1, 2, 3, 5, 8, ...?

• 11
• 13
• 16
• 10

Answer: 13. Each number is the sum of the two before it, so 5 + 8 = 13. Indian scholars such as Virahanka described these numbers centuries before Fibonacci's book of 1202.

Only one of these is a prime number. Which one?

• 51
• 57
• 87
• 89

Answer: 89. 89 has no factors other than 1 and itself. The others only look prime: 51 = 3 x 17, 57 = 3 x 19 and 87 = 3 x 29. Their digits add up to a multiple of 3, which gives them away.

A shirt's price goes up by 10% and later comes down by 10%. Compared with the original, the final price is:

• The same
• 1% higher
• 1% lower
• 10% lower

Answer: 1% lower. Take ₹100. A 10% rise makes it ₹110, and 10% off ₹110 is ₹11, leaving ₹99. The cut is taken on a bigger number, so you end up 1% lower.

What is the value of 0! (zero factorial)?

• 0
• Undefined
• 1
• Infinity

Answer: 1. 0! is defined as 1. That keeps the rule n! = n x (n - 1)! working, since 1! = 1 x 0!, and it matches the idea that there is exactly one way to arrange nothing.

How many diagonals does a hexagon have?

• 6
• 12
• 9
• 15

Answer: 9. Each of the 6 corners joins to the 3 corners that are not its neighbours: 6 x 3 = 18. Every diagonal gets counted twice, so 18 ÷ 2 = 9. The general formula is n(n - 3)/2.

Two ordinary dice are rolled. What is the chance that the two numbers add up to 7?

• 1/6
• 1/12
• 7/36
• 1/36

Answer: 1/6. There are 36 equally likely outcomes, and 6 of them make 7: (1,6), (2,5), (3,4), (4,3), (5,2) and (6,1). 6/36 = 1/6, which makes 7 the most likely total.

What is the smallest number that can be divided exactly by every whole number from 1 to 10?

• 720
• 1,260
• 5,040
• 2,520

Answer: 2,520. You need 2 x 2 x 2 (for 8), 3 x 3 (for 9), 5 and 7: 8 x 9 x 5 x 7 = 2,520. 5,040 (which is 7 x 6 x 5 x 4 x 3 x 2 x 1) also works, but it is twice as big.