Question: The area of a rectangular field (in m²) of length 55.3 m and breadth 25 m after rounding off the value for correct significant digits is: [PMT/NEET-2022]
a. 138×10¹
b. 1382
c. 1382.5
d. 14×10²

Solution:

We need the area:

$
A = \text{length} \times \text{breadth} = 55.3 \times 25
$

$
A = 1382.5 \ \text{m}^2
$

Now apply the rule of significant figures for multiplication:

• In multiplication/division, the result should have the same number of significant figures as the least among the measured quantities.
• $55.3$ has 3 significant figures.
• $25$ has 2 significant figures.
• Therefore, the final answer should have 2 significant figures.

Rounding $1382.5$ to 2 significant figures:

$
A = 1.4 \times 10^3 \ \text{m}^2
$

Answer: d. $14 \times 10^2$