GMAT Problem Solving- 16 Ounces of Birdseed Mix Contains 10% Sesame Seed by Weight

Question: 16 ounces of birdseed mix contains 10% sesame seed by weight. How much sesame seed must be added to produce a mix that is 20% sesame seed by weight?

  1. 1 ounce
  2. 1.6 ounces
  3. 2 ounces
  4. 2.4 ounce
  5. 4 ounces

“6 ounces of birdseed mix contains 10% sesame seed by weight.”- is a topic of the GMAT Quantitative reasoning section of GMAT. This question has been taken from the book “GMAT Quantitative Review”. To solve GMAT Problem Solving questions a student must have knowledge about a good amount of qualitative skills. The GMAT Quant topic in the problem-solving part requires calculative mathematical problems that should be solved with proper mathematical knowledge.

Solution and Explanation:

Approach Solution 1:

Given:

  • Total 16 ounces of birdseed mix
  • Contains 10% sesame seed by weight

To find:

  • Amount of sesame seed must be added to produce a mix that is 20% sesame seed by weight

We are going to take the following approach to solve the problem.

In the initial mix, the amount of sesame seed is:
= 16 * 0.1
= 1.6 ounces

Let us assume that the amount of sesame seed to be mixed is “M” ounces

Therefore, after mixing,

The amount of sesame seed = 1.6 + M
The total amount of mix = 16 + M

As per the problem statement, the sesame seed accounts for 20% of the total mix amount, we can write

(16 + M) * 20% = 1.6 + M

(16 + M) * 20/100 = 1.6 + M
=> 3.2 + 0.2M = 1.6 + M
=> 0.8M = 1.6
=> M = 2

Correct Answer: C

Approach Solution 2:

Given:

  • Total 16 ounces of birdseed mix
  • Contains 10% sesame seed by weight

To find:

  • Amount of sesame seed must be added to produce a mix that is 20% sesame seed by weight

We are going to take the following approach to solve the problem.

In 16 Ounces, we have 10% sesame seed i.e. 1.6 ounce.
Now, let us assume x ounce of sesame seed needed to make mixture that contains 20% of sesame seed
Hence, the equation stands:
=> (1.6+x)/(16+x)= 1/5
=> by cross-multiplication, 8+5x= 16+x
=> 4x=8
=> x=2

Correct Answer: C

Approach Solution 3:

Given:

16 ounces of mixed birdseed.
Contains 10% sesame seed in its composition.
To determine

To make a mixture that contains 20% sesame seed by weight, the right amount of sesame seed must be added.
The following approach will be used to solve the problem.

10% or 1.6 ounces of sesame seeds are present in 16 ounces.
Let's now assume that x ounces of sesame seeds are required to generate a combination with 20% sesame seeds.
As a result, the following equation is true:
=> (1.6+x)/(16+x)=1/5
=> via cross-multiplication, 8+5x= 16+x 
=> 4x=8 
=> x=2

Correct Answer: C

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