PSLE Lee and Rael have the same total number of coins. Lee has a number of twenty-cent coins and 55 ten-cent coins. The total mass of his coins is 0.562 kg. Rael has a number of twenty-cent coins and 115 ten-cent coins.
- Who has less money in coins? How much less? Give your answers in this format. (Eg Adam, $12)
- Each twenty-cent coin is 2.8 g heavier than each ten-cent coin. What is the total mass of Rael's coins in kg?
(a)
Both boys have the same number of coins. Since Rael has more ten-cent coins than Lee, it means that Rael has less twenty-cent coins than Lee. So Rael has less money.
Difference in the number of ten-cent coins.
= 115 - 55
= 60
Difference in the value of 1 ten-cent coin and 1 twenty-cent coin
= 20 - 10
= 10¢
Amount that Rael had less than Lee
= 60 x 10
= 600¢
= $6
(b)
Difference in the mass between 60 ten-cent coins and 60 twenty-cent coins
= 60 x 2.8
= 168 g
= 0.168 kg
Total mass of Rael's coins
= 0.562 - 0.168
= 0.394 kg
Answer(s): (a) Lee, $6; (b) 0.394 kg