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# In a forest, the ratio of pine trees to maple trees if 7:3, and the ra

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In a forest, the ratio of pine trees to maple trees if 7:3, and the ra  [#permalink]

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09 Apr 2018, 01:11
00:00

Difficulty:

5% (low)

Question Stats:

95% (00:56) correct 5% (01:21) wrong based on 60 sessions

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In a forest, the ratio of pine trees to maple trees if 7:3, and the ratio of oak trees to maple trees is 5:2. What is the ratio of pine trees to oak trees?

A. 7:5
B. 5:7
C. 7:10
D. 14:15
E. 15:14

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Re: In a forest, the ratio of pine trees to maple trees if 7:3, and the ra  [#permalink]

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09 Apr 2018, 01:23
Bunuel wrote:
In a forest, the ratio of pine trees to maple trees if 7:3, and the ratio of oak trees to maple trees is 5:2. What is the ratio of pine trees to oak trees?

A. 7:5
B. 5:7
C. 7:10
D. 14:15
E. 15:14

Multiple ways to solve this one. I will use the make common part of proportion same approach.

Pine : Maple = 7 : 3
Oak : Maple = 5 : 2

Multiple the first proportion by 2 and the second by 3 & combine.

Pine : Maple : Oak = 14 : 6 : 15

Drop the Maple which served us as a bridge between Pine and Oak which is the question stem

Pine : Oak = 14 : 15

Hence Option (D) is our answer.

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Re: In a forest, the ratio of pine trees to maple trees if 7:3, and the ra  [#permalink]

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09 Apr 2018, 01:26
P : M = 7 : 3
M : O = 2 : 5
P :M : O = 14 : 6 : 15

Hence, P : O = 14 : 15 ( option D)

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Posts: 2457
Re: In a forest, the ratio of pine trees to maple trees if 7:3, and the ra  [#permalink]

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09 Apr 2018, 23:33

Solution

Given:

Let us denote pine tree by ‘p’, maple trees by ‘m’, and oak trees by ‘o’.

• p:m= 7:3--------(1)
• o: m = 5:2-------(2)

To find:
• We need to find the ratio of pine trees to oak trees i.e. p:o.

Approach and Working:

• By taking inverse of equation (2), we can write:
• m: o =2:5---------(3)

• By multiplying equation (1) and equation (3), we can write:
• p:m *m:o =7:3 * 2:5=14:15
• p:o= 14:15

Thus, the ratio of pine trees to oak trees is 14:15.

Hence, the correct answer is option D.

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Re: In a forest, the ratio of pine trees to maple trees if 7:3, and the ra  [#permalink]

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11 Apr 2018, 15:21
Bunuel wrote:
In a forest, the ratio of pine trees to maple trees if 7:3, and the ratio of oak trees to maple trees is 5:2. What is the ratio of pine trees to oak trees?

A. 7:5
B. 5:7
C. 7:10
D. 14:15
E. 15:14

We are given that the ratio of pine trees to maple trees is 7:3 and that the ratio of oak trees to maple trees is 5:2. Thus:

pine trees : maple trees = 7 : 3

and

oak trees : maple trees = 5 : 2

We can manipulate the first ratio by multiplying by 2 and we have:

pine trees : maple trees = 14 : 6

We can manipulate the second ratio by multiplying by 3 and we have:

oak trees : maple trees = 15 : 6

Thus, the ratio of pine trees to oak trees is 14 : 15.

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Re: In a forest, the ratio of pine trees to maple trees if 7:3, and the ra &nbs [#permalink] 11 Apr 2018, 15:21
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