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# John and his dad were calculating the ratios of their ages.

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John and his dad were calculating the ratios of their ages.  [#permalink]

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Updated on: 21 Aug 2018, 23:04
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Difficulty:

45% (medium)

Question Stats:

56% (02:07) correct 44% (02:23) wrong based on 24 sessions

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John and his dad were calculating the ratios of their ages. Currently, John's dad is four times as old as John. Eight years later, John's dad will be two and half times of John's age. What will be the ratio of John and John's dad 32 years later?

1) 5:8
2) 1:4
3) 8:5
4) 4:7
5) 7:4

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Originally posted by Chethan92 on 21 Aug 2018, 10:32.
Last edited by Chethan92 on 21 Aug 2018, 23:04, edited 1 time in total.
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John and his dad were calculating the ratios of their ages.  [#permalink]

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Updated on: 22 Aug 2018, 10:38
Let John's Dad be X and John be Y

1) X = 4Y -----------------------> Now
2) X+8 = 2.5(Y + 8) --------------> 8 years later
4Y + 8 = 2.5(Y + 8) ------------> substituting 1) in 2)
1.5Y = 12
Y = 8
so X = 32

3) (X + 32) /(Y+ 32) ---------------> 32 years later
(32 + 32) /(8 +32)
64 / 40
8/5

Edited:

This is wrong upto now the ratio is between John' dad to john and the question is other way.

Originally posted by magbot on 21 Aug 2018, 11:00.
Last edited by magbot on 22 Aug 2018, 10:38, edited 2 times in total.
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Re: John and his dad were calculating the ratios of their ages.  [#permalink]

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21 Aug 2018, 23:02
Afc0892 wrote:
John and his dad were calculating the ratios of their ages. Currently, John's dad is four times as old as John. Eight years later, John's dad will be two and half times of John's age. What will be the ratio of John and John's dad 32 years later?

1) 5:8
2) 1:4
3) 8:5
4) 4:7
5) 7:4

Hi Afc0892,

The answer should be A as the ratio of John & John's Dad = $$40/64.$$ = $$5/8$$
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NUS School Moderator
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Posts: 990
Location: India
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Re: John and his dad were calculating the ratios of their ages.  [#permalink]

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21 Aug 2018, 23:05
rahul16singh28 wrote:
Afc0892 wrote:
John and his dad were calculating the ratios of their ages. Currently, John's dad is four times as old as John. Eight years later, John's dad will be two and half times of John's age. What will be the ratio of John and John's dad 32 years later?

1) 5:8
2) 1:4
3) 8:5
4) 4:7
5) 7:4

Hi Afc0892,

The answer should be A as the ratio of John & John's Dad = $$40/64.$$ = $$5/8$$

Edited, thanks

Posted from my mobile device
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Re: John and his dad were calculating the ratios of their ages.  [#permalink]

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21 Aug 2018, 23:10
Afc0892 wrote:
John and his dad were calculating the ratios of their ages. Currently, John's dad is four times as old as John. Eight years later, John's dad will be two and half times of John's age. What will be the ratio of John and John's dad 32 years later?

1) 5:8
2) 1:4
3) 8:5
4) 4:7
5) 7:4

present ratio ..
$$J:D = x:4x..$$

ratio after 8 years
$$J+8:D+8 = x+8:4x+8=1:2.5,.........\frac{x+8}{4x+8}=\frac{1}{2.5}=\frac{2}{5}..........5x+40=8x+16........x=8$$

ratio after 32 years
$$J+32:D+32 = x+32:4x+32=8+32:4*8+32=40:64=5:8..$$

A
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Re: John and his dad were calculating the ratios of their ages.   [#permalink] 21 Aug 2018, 23:10
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