PSLE
Ken and Vincent have the same total number of coins. Ken has a number of twenty-cent coins and 60 ten-cent coins. The total mass of his coins is 0.63 kg. Vincent has a number of twenty-cent coins and 100 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 2.8 g heavier than each ten-cent coin. What is the total mass of Vincent's coins in kg?

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

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

Difference in the number of ten-cent coins.
= 100 - 60
= 40

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

Amount that Ken had more than Vincent
= 40 x 10
= 400¢
= $4

(b)
Difference in the mass between 40 ten-cent coins and 40 twenty-cent coins
= 40 x 2.8
= 112 g
= 0.112 kg

Total mass of Vincent's coins
= 0.63 - 0.112
= 0.518 kg

Answer(s): (a) Ken, $4; (b) 0.518 kg