NCERT Solutions Class 11 Physics - Solved Exercise Question 2.11

Question 2.11:

The length, breadth and thickness of a rectangular sheet of metal are 4.234 m, 1.005 m, and 2.01 cm respectively. Give the area and volume of the sheet to correct significant figures.

Solution:

Length of sheet, l = 4.234 m
Breadth of sheet, b = 1.005 m
Thickness of sheet, h = 2.01 cm = 0.0201 m

The given table lists the respective significant figures:

Quantity
Number
Significant Figure
l
4.234
4
b
1.005
4
h
0.0201
3

Hence, area and volume both must have least significant figures i.e., 3.
Surface area of the sheet = 2 (l × b + b × h + h × l)
= 2(4.234 × 1.005 + 1.005 × 0.0201 + 0.0201 × 4.234)
= 2(4.25517 + 0.0202005 + 0.0851034)
= 2 × 4.36
= 8.72 m2
Volume of the sheet = l × b × h
= 4.234 × 1.005 × 0.0201
= 0.0855 m3

This number has only 3 significant figures i.e., 8, 5, and 5.

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