Question

A student wants to measure the thickness of a single sheet of paper. He measures the thickness of the stack of 75 sheets with a micrometer and registers the reading as 1.16cm. The thickness of a single sheet should be expressed correctly as-

• A. 0.15467mm
• B. 0.1547mm
• C. 0.155 mm
• D. 0.15 mm.

Answer 1

Answer: (A)

0.15467mm

Answer 2

Thickness of 1 sheet of paper = 1.16/75 cm

= 0.0154666 mm

When a measured quantity is multiplied or divided by a exact number, the result should not contain significant digits more than the measured quantity, i.e. it should contain significant figures equal to the significant figures of the measured quantity.

Here 75 is a exact number and measured quantity 1.16 cm contains three significant figures. Therefore after rounding off properly answer should be expressed in three significant figures.