PSLE Ken and Justin have the same total number of coins. Ken has a number of twenty-cent coins and 45 ten-cent coins. The total mass of his coins is 0.637 kg. Justin has a number of twenty-cent coins and 105 ten-cent coins.
- Who has more money in coins? How much more? Give your answers in this format. (Eg Adam, $12)
- Each twenty-cent coin is 1.4 g heavier than each ten-cent coin. What is the total mass of Justin's coins in kg?
(a)
Since Ken has less ten-cent coins than Justin 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 Justin, it means that Ken has more twenty-cent coins than Justin. So Ken has more money.
Difference in the number of ten-cent coins.
= 105 - 45
= 60
Difference in the value of 1 ten-cent coin and 1 twenty-cent coin
= 20 - 10
= 10¢
Amount that Ken had more than Justin
= 60 x 10
= 600¢
= $6
(b)
Difference in the mass between 60 ten-cent coins and 60 twenty-cent coins
= 60 x 1.4
= 84 g
= 0.084 kg
Total mass of Justin's coins
= 0.637 - 0.084
= 0.553 kg
Answer(s): (a) Ken, $6; (b) 0.553 kg