Question

A table top measures 3 m 15 cm by 90 cm. The perimeter of the table top is
(a) 4 m 5 cm
(b) 8 m 10 cm
(c) 24 m 30 cm
(d) None of these

Answer 1

Hint: To solve this question, we will find the length and breadth of the table top in a uniform unit, say centi-meter. The perimeter of a rectangle is defined as the sum of all sides or 2(length + breadth). Then we will convert the perimeters in centi-meter units to the required units to match our options.

Complete step-by-step answer:
The measurement of the table top is given as 3 m 15 cm by 90 cm. This means that the length of the table top is 3 m 15 cm and breadth is 90 cm.
As we know, 1 m = 100 cm. Keeping this conversion in mind, we shall now convert 3 m 15 cm in centi-meters.
$\Rightarrow $ 3 m 15 cm = [3(100) + 15] cm
$\Rightarrow $ [300 + 15] cm = 315 cm
Now, the length of the table top is 315 cm.
We shall calculate the perimeter now with the formula P = 2(l + b), where P is perimeter, l is the length and b is the breadth. We will substitute l = 315 cm and b = 90 cm.
$\Rightarrow $ P = 2(315 + 90) cm
$\Rightarrow $ P = 2(405) cm
$\Rightarrow $ P = 810 cm
Now, 810 cm can also be written as 800 cm + 10 cm. But as we know, 100 cm = 1 m, 800 cm will change to 8 m.
Therefore, the perimeter of the table top is 8 m 10 cm.
Hence, option (b) is the correct option.

Note: The importance of this question lies in the unit conversion and therefore students are advised to be well-versed with all the basic unit conversions to be perfect in these types of questions.