Question

Ritu was building a tower of LEGO blocks. She placed 4 blocks on the tower every minute, and took 60 minutes to finish the tower. When her brother joined her, together they were able to place 8 blocks on the tower for every minute. How long will it take to complete the tower now?

A
30 minutes
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B
15 minutes
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C
45 minutes
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D
20 minutes
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Solution

The correct option is C 30 minutesIf more people help out in the tower construction, it will take lesser time. ∴ This is a case of inverse proportion. Using the formula for inverse proportion, Number of blocks× Time required= constant ⇒ 4 × 60 = 8 × Time required ∴ Time required = 4 × 608 = 30 minutes

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