If 80 Lamps Can Be Lighted, 5 Hours Per Day For 10 Days GMAT Problem Solving

Question: If 80 lamps can be lighted, 5 hours per day for 10 days for $21.25, then the number of lamps, which can be lighted 4 hours daily for 30 days, for $76.50, is

1. 100
2. 120
3. 150
4. 160
5. 180

“If 80 Lamps Can Be Lighted, 5 Hours Per Day For 10 Days GMAT Problem Solving” - 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.

Solution and Explanation:

Approach Solution:

There is only 1 approach to solving this problem

Explanation: this question comes with only one approach to solve lets see that approach below-
to find the number of lamps, which can be lighted 4 hours daily for 30 days, for $76.50, let's try to evaluate the question,
It is given that –
80 lamps can be lighted, 5 hours per day for 10 days for $21.25
Now Let the required number of lamps be x.
Lets us apply direct proportion and indirect proportion to solve the question further-
Less hours per day means More lamps (Indirect Proportion)
More money means More lamps (Direct Proportion)
More days means Less lamps (Indirect Proportion)
hours/days = 4 : 5 :: 80 : x
Hours = 21.25 : 76.50 :: 80 : x
Number of days = 30 : 10 :: 80 : x
Therefore,
4 × 21.25 × 30 × x = 5 × 76.50 × 10 × 80
x = 120
The correct answer is B which is 120

Correct Answer: B

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