# 12 Pipes, All of the Same Size, Fill a Tank in 42 Minutes. How Long Will It Take to Fill the Same Tank, If 21 Pipes of the Same Size Are Used? - Mathematics

Sum

12 pipes, all of the same size, fill a tank in 42 minutes. How long will it take to fill the same tank, if 21 pipes of the same size are used?

#### Solution

Pipes: Time:: Pipes: Time

12  :    2x  ::   21  :  42

∴ By inverse proportion

12 × 42 = 21 × x

⇒"x"=(12xx42)/21

= 24 minutes

Concept: Time and Work
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#### APPEARS IN

Selina Concise Mathematics Class 8 ICSE
Chapter 10 Direct and Inverse Variations
Exercise 10 (B) | Q 4 | Page 123