PSLE
Xavier and Bobby have the same total number of coins. Xavier has a number of twenty-cent coins and 64 ten-cent coins. The total mass of his coins is 1.006 kg. Bobby has a number of twenty-cent coins and 124 ten-cent coins.

1. Who has more money in coins? How much more? Give your answers in this format. (Eg Adam, $12)
2. Each twenty-cent coin is 1.1 g heavier than each ten-cent coin. What is the total mass of Bobby's coins in kg?

(a)
Since Xavier has less ten-cent coins than Bobby but both had the same number of coins, Xavier had more money.

Both boys have the same number of coins. Since Xavier has less ten-cent coins than Bobby, it means that Xavier has more twenty-cent coins than Bobby. So Xavier has more money.

Difference in the number of ten-cent coins.
= 124 - 64
= 60

Difference in the value of 1 ten-cent coin and 1 twenty-cent coin
= 20 - 10
= 10¢

Amount that Xavier had more than Bobby
= 60 x 10
= 600¢
= $6

(b)
Difference in the mass between 60 ten-cent coins and 60 twenty-cent coins
= 60 x 1.1
= 66 g
= 0.066 kg

Total mass of Bobby's coins
= 1.006 - 0.066
= 0.94 kg

Answer(s): (a) Xavier, $6; (b) 0.94 kg