rajatvmittal wrote:A grocery store bought some mangoes at a rate of 5 for a dollar. They were separated into two stacks, one of which was sold at a rate of 3 for a dollar and the other at a rate of 6 for a dollar. What was the ratio of the number of mangoes in the two stacks if the store broke even after having sold all of its mangoes?
1:4
1:5
2:3
1:2
2:5
Correct Answer A
Let C = the cost of each mango, H = the higher selling price, and L = the lower selling price.
Since the mangos are purchased at 5 per dollar, C = 1/5 of a dollar.
Since the higher selling price is 3 per dollar, H = 1/3 of a dollar.
Since the lower selling price is 6 per dollar, L = 1/6 of a dollar.
To break even when the mangos are sold, the average revenue per mango must be equal to C = 1/5 of a dollar.
This is a MIXTURE problem.
A selling price of 1/3 of a dollar (H) is MIXED with a selling price of 1/6 of a dollar (L) to yield an AVERAGE revenue of 1/5 of a dollar (C).
Use ALLIGATION -- a great way to handle mixture problems.
Step 1: Put the fractions over a COMMON DENOMINATOR.
C = 1/5 = 6/30.
H = 1/3 = 10/30.
L = 1/6 = 5/30.
Step 2: Plot the 3 NUMERATORS on a number line, with the numerators for the selling prices (10 and 5) on the ends and numerator for the average revenue (6) in the middle.
H 10-----------6-----------5 S
Step 3: Calculate the distances between the numerators.
H 10-----
4-----6-----
1-----5 S
Step 4: Determine the ratio of H to L in the mixture.
The required ratio of H to L is equal to the RECIPROCAL of the distances in red.
H:L = 1:4.
The correct answer is
A.
For two other problems that I solved with alligation, check here:
https://www.beatthegmat.com/ratios-fract ... tml#484583
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