PSLE
Bobby and Justin have the same total number of coins. Bobby has a number of twenty-cent coins and 50 five-cent coins. The total mass of his coins is 0.901 kg. Justin has a number of twenty-cent coins and 110 five-cent coins.

1. Who has less money in coins? How much less? Give your answers in this format. (Eg Adam, $12)
2. Each twenty-cent coin is 2.5 g heavier than each five-cent coin. What is the total mass of Justin's coins in kg?

(a)
Both boys have the same number of coins. Since Justin has more five-cent coins than Bobby, it means that Justin has less twenty-cent coins than Bobby.  So Justin has less money.

Difference in the number of five-cent coins.
= 110 - 50
= 60

Difference in the value of 1 five-cent coin and 1 twenty-cent coin
= 20 - 5
= 15¢

Amount that Justin had less than Bobby
= 60 x 15
= 900¢
= $9

(b)
Difference in the mass between 60 five-cent coins and 60 twenty-cent coins
= 60 x 2.5
= 150 g
= 0.15 kg

Total mass of Justin's coins
= 0.901 - 0.15
= 0.751 kg

Answer(s): (a) Bobby, $9; (b) 0.751 kg