Mr Nizam's e-classroom
Mathematics & Science
Ratio Word Problems
Covered in Primary 5, some of the common ratio word problems are one-quantity unchanged, unchanged total and unchanged difference.
1) One-quantity unchanged
When to use this method?
When one of the item did not change throughout the question (from the start to the end of the question)
Example question:
Ali and Ahmad had marbles in the ratio of 4:7.
During a match, Ahmad loses 15 marbles and their marbles became a ratio of 2:3.
How many marbles did Ali have at first?
Think:
1) For ratio word problems, you have to ask yourself "What did not change?"
2) In this question, logically what does not change?
(Answer : Ali's marble did not change because only Ahmad loses 15 marbles.)
3) So since Ali's marble did not change, we have to make Ali's marbles the same before & after the match
Solution: Click here
2) Unchanged total
When to use this method?
When the exchange is just between the people/item in the question only
Example question:
Kamal and Norman had sweets in the ratio of 5:7.
After Kamal gave Norman 21 of his sweets, the ratio became 1:5.
How many sweets did Kamal have at first?
Think:
1) For ratio word problems, you have to ask yourself "What did not change?"
2) In this question, logically what does not change? (Answer : The total number of sweets of Kamal & Norman did not change)
3) So since their total sweets did not change, we have to make the total units for before & after the same
Solution: Click here
3) Unchanged difference
When to use this method?
When the increment or decrement for all the people/item in the question is always the same
Example question:
Khairul and Faizal had sweets in the ratio of 5:11.
After each of them get 70 extra sweets, the ratio became 2:3.
How many sweets did Faizal have in the end?
Think:
1) For ratio word problems, you have to ask yourself "What did not change?"
2) In this question, logically what does not change?
(Answer : Since both of them get 70 extra sweets each, the difference between both of them will remind the
same)
3) So since their difference in the number of sweets are the same, we have to make the difference in terms of
units for before & after the same
Solution: Click here