Water Consists of Hydrogen and Oxygen, and the Approximate GMAT Problem Solving

Question: Water consists of hydrogen and oxygen, and the approximate ratio, by mass, of hydrogen to oxygen is 2 : 16. Approximately how many grams of oxygen are there in 144 grams of water?

1. 16
2. 72
3. 112
4. 128
5. 142

Answer:

Approach Solution (1):

Since the ratio, by mass, of hydrogen to oxygen is 2 : 16, then oxygen is \(\frac{16}{(2+16)}=\frac{8}{9}\) of mass of water.

Therefore, there are \(\frac{144*8}{9}=128\) grams of oxygen in 144 grams of water.

Correct option: D

Approach Solution (2):

Given ratio: 2 : 16 = 1 : 8 = Hydrogen : Oxygen

Let the quantity = x (by mass)

x + 8x = 144
x = 16

Amount of oxygen = 144 – 16 = 128

Correct option: D

“Water consists of hydrogen and oxygen, and the approximate ratio, by mass, of hydrogen to oxygen is 2 : 16. Approximately how many grams of oxygen are there in 144 grams of water?”- is a topic of the GMAT Quantitative reasoning section of GMAT. This question has been taken from the book “GMAT Official Guide 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.

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