## Q&A - P5 Math

### Re: Q&A - P5 Math

Can someone please help with this question please.. Thank you very much in advance..

Peter's age is 1/7 of his grandmother's. His grandmother will be 89 years old in 5 years time. In how many years time will Peter's age be 5/9 of his grandmother's?

Peter's age is 1/7 of his grandmother's. His grandmother will be 89 years old in 5 years time. In how many years time will Peter's age be 5/9 of his grandmother's?

### Re: Q&A - P5 Math

Hi belnanna,belnanna wrote:Can someone please help with this question please.. Thank you very much in advance..

Peter's age is 1/7 of his grandmother's. His grandmother will be 89 years old in 5 years time. In how many years time will Peter's age be 5/9 of his grandmother's?

His grandmother is 89 - 5 = 84 years old now.

So, Peter is 1/7 of 84 = 12 years old now.

Age difference = 84 - 12 = 72 years old (constant difference)

For Peter to be 5/9 of his grandmother's age, the difference will be 4/9 = 72

----------- => 5/9 = 72/4 x 5 = 90

Therefore, Peter should be 90 years old and grandmother 162 years old for him to be 5/9 of her age.

Ans: 90 - 12 =

**78**years' time

(The answer does not seem to be "realistic" but should be mathematically correct.)

cheers...

### Re: Q&A - P5 Math

Thank you dear.tanxexy wrote:Hi belnanna,belnanna wrote:Can someone please help with this question please.. Thank you very much in advance..

Peter's age is 1/7 of his grandmother's. His grandmother will be 89 years old in 5 years time. In how many years time will Peter's age be 5/9 of his grandmother's?

His grandmother is 89 - 5 = 84 years old now.

So, Peter is 1/7 of 84 = 12 years old now.

Age difference = 84 - 12 = 72 years old (constant difference)

For Peter to be 5/9 of his grandmother's age, the difference will be 4/9 = 72

----------- => 5/9 = 72/4 x 5 = 90

Therefore, Peter should be 90 years old and grandmother 162 years old for him to be 5/9 of her age.

Ans: 90 - 12 =78years' time

(The answer does not seem to be "realistic" but should be mathematically correct.)

cheers...

### Re: Q&A - P5 Math

Hi belnanna, you are welcomedbelnanna wrote: Thank you dear.

Btw, where did this question come from? It is rather "cruel" as a child might be puzzling where he had gone wrong when he got such "bizarre" ages as answers. He might start to doubt himself and try to work out a different approach towards getting a more "realistic" answer.

On the other hand, this question also challenges the students to be very sound with their mathematical understanding and have the confidence to stand by it.

cheers...

### Re: Q&A - P5 Math

Hi,tanxexy wrote:Hi belnanna, you are welcomedbelnanna wrote: Thank you dear.

Btw, where did this question come from? It is rather "cruel" as a child might be puzzling where he had gone wrong when he got such "bizarre" ages as answers. He might start to doubt himself and try to work out a different approach towards getting a more "realistic" answer.

On the other hand, this question also challenges the students to be very sound with their mathematical understanding and have the confidence to stand by it.

cheers...

Its from a future school in Bukit Panjang in the form of a practice paper..

### Re: Q&A - P5 Math

I see...btw, what do you mean by "future school"? The school is not officially opened yet?belnanna wrote:Hi,tanxexy wrote:Hi belnanna, you are welcomedbelnanna wrote: Thank you dear.

Btw, where did this question come from? It is rather "cruel" as a child might be puzzling where he had gone wrong when he got such "bizarre" ages as answers. He might start to doubt himself and try to work out a different approach towards getting a more "realistic" answer.

On the other hand, this question also challenges the students to be very sound with their mathematical understanding and have the confidence to stand by it.

cheers...

Its from a future school in Bukit Panjang in the form of a practice paper..

### Re: Q&A - P5 Math

triangle BPC is 1/4 of the rectangle. (because P is the midpoint of the width)Daddy wrote:Hi all,

I have 2 questions to ask.

THANK ALL..

so the rectangle's area is 24 x 4 = 96

the area of triangle QPD should be 2/3 of 24 = 16

area of quad = 96 - 24 - 16 - 16 = 40

### Re: Q&A - P5 Math

if you let 100% be 10 units, thenDaddy wrote:Hi all,

I have 2 questions to ask.

THANK ALL..

10B = 10G + 90

after 80% B and 30% girls left

--> 2B + 18 (boys left)

--> 7G (girls left)

7G = 4B + 36 ( girls are twice number of boys left)

10B = 10G + 90 -> 1B = 1G + 9 -> 4B = 4G + 36

so

7G = (4G + 36 ) + 36

3G = 72

1G = 24

1B = 24 + 9 = 33

10B + 90 = 330 + 90 = 420 (ans)

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### Re: Q&A - P5 Math

jojoberry wrote:triangle BPC is 1/4 of the rectangle. (because P is the midpoint of the width)Daddy wrote:Hi all,

I have 2 questions to ask.

THANK ALL..

so the rectangle's area is 24 x 4 = 96

the area of triangle QPD should be 2/3 of 24 = 16

area of quad = 96 - 24 - 16 - 16 = 40

Hi,

The area of triangle QPD should be

**3/4**of 24 =

**18**

area of quad = 96 - 24 - 16 - 18 =

**38**

Hope this helps.

Cheers

**speedmaths**

.