Question

Q. A room measure 3m 55cm by 2m 25 cm. What is the perimeter of the room?

Ans. Given L=3m,55cm
B=2m,25cm
Perimeter = 2(l+b)
=2 (3m,55cm + 2m, 25cm)
3m 55cm
2m 25cm +
_____________
5m 80cm
______________
2×(5cm,80) 5×2=10 , 80×2=160
So 10m 160cm
but the answer is 11m 60 cm why and how to convert?​

Answer 1

100cm = 1m

Thus, one more step should be added to your working to arrive at the final answer:

Perimeter

= 10m 160cm

= 11m 60cm

This is because 160cm= 100cm +60cm, which is also equivalent to 1m 60cm.

Alternative working:

Convert all the units to cm first.

`\boxed{1 \: m= 100 \: cm}`

Length

= 5m 55cm

= 300cm +55cm

= 355cm

Breadth

= 2m 25cm

= 200cm +25cm

= 225cm

Perimeter

= 2(length +breadth)

= 2(355 cm +225 cm)

= 2(580 cm)

= 1160 cm

= 11m 60cm

From the second last step to the last step, you could divide 1160 by 100 to find how many meters are there. You would get a quotient of 11 and a remainder of 60. Since this 60 cannot be changed into meters as a whole number, we can leave it as 11m 60cm. Otherwise, it is also correct to leave it as 1160cm or 11.6m unless otherwise stated.

However, 10m 160cm is not preferred since the conversion of cm to m is done partially, as the 160 cm can still be further simplified.