Maths-

General

Easy

Question

# Two solid cylinders with radii 5 cm and 10 cm and lengths of 7 cm and 5 cm respectively are melted and recast into a cylindrical disc of thickness 3 cm, Calculate its radius.

Hint:

### We calculate volumes of both solid cylinders and take the sum. Thickness of the disc will act as the height of the disc and from that equation we find the radius.

## The correct answer is: The required radius is 15 cm.

### Explanations:

Step 1 of 2:

Volume of the cylinder is

Total volume = cm^{3}

Step 2 of 2:

Let the radius of the re-casted cylindrical disc be R .

Thickness of disc = height of disc = 3 cm

Volume of disc =

, discarding the negative since distance is always positive

Final Answer:

The required radius is 15 cm.

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