PSLE
Bobby and Billy have the same total number of coins. Bobby has a number of fifty-cent coins and 66 five-cent coins. The total mass of his coins is 0.559 kg. Billy has a number of fifty-cent coins and 86 five-cent coins.

1. Who has less money in coins? How much less? Give your answers in this format. (Eg Adam, $12)
2. Each fifty-cent coin is 2.9 g heavier than each five-cent coin. What is the total mass of Billy's coins in kg?

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

Difference in the number of five-cent coins.
= 86 - 66
= 20

Difference in the value of 1 five-cent coin and 1 fifty-cent coin
= 50 - 5
= 45¢

Amount that Billy had less than Bobby
= 20 x 45
= 900¢
= $9

(b)
Difference in the mass between 20 five-cent coins and 20 fifty-cent coins
= 20 x 2.9
= 58 g
= 0.058 kg

Total mass of Billy's coins
= 0.559 - 0.058
= 0.501 kg

Answer(s): (a) Bobby, $9; (b) 0.501 kg