Question

The length,breadth and thickness of a rectangular copper sheet are $4cm,2.5cm$ and $1.56cm$ respectively. Find the area of the sheet to corrected significant figures.

• A. $40.3c{m}^2$
• B. $40.28c{m}^2$
• C. $40\times {10}^{2}c{m}^2$
• D. $0.4\times {10}^{2}c{m}^2$

Answer 1

Answer: (D)

$0.4\times {10}^{2}c{m}^2$

If $l$ be the length, $b$ be the breadth and $t$ be the thickness of the sheet,
then the area of sheet is $A=2(lb+bt+tl)=2\left[\right(4\times 2.5)+(2.5\times 1.56)+(1.56\times 4\left)\right]=40.28c{m}^2$
As length has least significant figures i.e one so the answer must be expressed as one significant figures.
Thus according rule of determining significant figures, the area will be $0.4\times {10}^{2}c{m}^2$