Question

If 45mm is expressed in cm then answer is 4.5 cm
$
  (a){\text{ True}} \\
  (b){\text{ False}} \\
 $

Answer 1

Hint: In this question we have to tell whether conversion of 45mm into cm is 4.4 cm or not. Use the basic unit system conversion rule that 1cm = 10mm. Then use the unitary method to convert 45mm into cm using this unit system conversion rule.

Complete step-by-step answer:
As we know 1mm = $\dfrac{1}{{1000}}$m
And 1 m = 100 cm, so use this property in above equation we have,
Therefore 1 mm = $\left( {\dfrac{1}{{1000}}} \right)\left( {100{\text{ cm}}} \right)$
Now cancel out two zero from numerator and denominator we have,
$ \Rightarrow 1{\text{ mm = }}\dfrac{1}{{10}}{\text{ cm}}$
Now we have to find out the value of 45 mm.
So multiply the above equation by 45 then we have,
$ \Rightarrow 45{\text{ mm = 45}} \times \left( {\dfrac{1}{{10}}{\text{ cm}}} \right)$
Now as we know $\dfrac{{45}}{{10}} = 4.5$ so use this property in above equation we have,
$ \Rightarrow 45{\text{ mm = 4}}{\text{.5 cm}}$
Hence the given problem statement is true.
Hence option (A) is correct.

Note: Whenever we face such types of problems the key concept is to have the basic understating of the unit system for length measurement. Using this system every unit for measurement of length can be converted into another. This concept will help to get on the right track to get the answer.