The following maths question came out in the recent Singapore Primary School Leaving Examination (PSLE) which are for 12- years-old.
NB: You cannot use algebra to solve the question, only via arithmetic methods.
Shop A has 156kg of rice. Shop B has 72kg of rice.
After both shops sold an equal amount of rice, the ratio of rice that shop A has to that of shop B is 4:1.
Find the amount of rice sold by the shops.
So far the only method I could come up with is to start using the 4:1 ratio.
You can start listing all multiples of 4:1, 8:2, 12:3 to a max of 156:39 and you start subtracting from the original amounts till you get the difference to be equal.
When you come to 112:28, 156-112=44 and 72-28=44, hence the answer is 44kg.