# A child's mobile makes one full rotation every 15 seconds. Through what angles has the mobile rotated after 5 minutes? Options are below.?

a. 2pi radians

b. 20pi radians

c. 40pi radians

d. 0 pi radians

### 5 Answers

- Iggy RockoLv 78 months ago
5 min = 5 * 60 = 300 s

300/15 = 20 rotations

20 rotations * 2pi/rotation = 40pi radians

- KrishnamurthyLv 78 months ago
A child's mobile makes one full rotation every 15 seconds.

Through what angles has the mobile rotated after 5 minutes?

The number of 15 seconds in 5 minutes is 20.

Answer option:

c. 40pi radians

- L. E. GantLv 78 months ago
15 seconds = 1/4 minute

5 minutes = 20 * 15 seconds

so 20 revolutions

1 revolution = 2pi radians

so 40pi radians

- stanschimLv 78 months ago
5 minutes x (60 seconds / 1 minute) = 300 seconds.

300 / 15 = 20 rotations.

1 rotation = 2π radians.

20 rotations = 40π radians (c).

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- PuzzlingLv 78 months ago
1 full rotation is 360° or 2π radians.

Intuitively:

In 1/4 minute (15 seconds) --> 2π radians.

In 1 minute --> 8π radians

In 5 minutes --> 40π radians

If you want to be a little more formal:

2π radians / 15 seconds * 60 seconds / minute * 5 minutes

= (2π * 60 * 5) / 15 radians

= 2π * 4 * 5 radians

= 40π radians

Answer:

c. 40π radians