Previously someone helped me by assuming Mabel is 1 year old and solve the quest

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primary 5 | Maths | Fractions
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primary 5 Maths Fractions Singapore

Previously someone helped me by assuming Mabel is 1 year old and solve the question. But my friend say can’t do that so can someone help me to verify please. Thanks

Date Posted: 5 years ago

Comments 3 add a comment

5 years ago

Since Mabel's age now is ¼ of her sister's age now,

We let Mabel's age now be 1 unit.
Sister's age now = 4 units

Mabel's age in 4 years' time = 1 unit + 4
Sister's age in 4 years' time = 4 units + 4

However question says her age in 4 years' time is ½ of her sister's age in 4 years' time. This also means that in 4 years' time, her sister's age is twice of her age.

So her sister's age in 4 years also = 2 x (1 units + 4)
= 2 units + 8

So 2 units + 8 = 4 units + 4

2 units + 8 = 2 units + 2 units + 4

From this we can determine that 2 units = 4 years

So 1 unit = 4 years ÷ 2 = 2 years

Mabel's sister's age in 4 years
= 4 units + 4
= 4 x 2 + 4
= 8 + 4
= 12

5 years ago

I believe you deleted my previous answer to your question, so here I have rewritten it.

We don't assume that Mabel's age is 1 year old. 1 unit does not mean 1 year old.

If you realised, Mabel's age now is actually 2 years old

Shervon

5 years ago

Oic ok thanks a lot.
Yes I accidentally deleted it when trying to post a new question.