Length and breadth of a rectangular board are 20cm and 50 cm. Find area of board in MKS unit?

Hint: First by using the formula for the area of a rectangle, find the area of the rectangular board with the given values of length and breadth. Then by using relation between centimetre and metre, find the area of the board in the MKS units.

Complete answer:
Let the length and breadth of a rectangle be l and b respectively. Then the area of a rectangle is given as A = lb.
It is given that the length and breadth of the rectangular board are 20cm and 50cm. This means that l = 20cm and b = 50cm.
Then the area of the rectangular board will be A = lb =$20cm\times 50cm=1000c{{m}^{2}}$ ……. (i).
In the MKS system of units, the unit of length is metres (m). But the given lengths are in the unit of centimetre (cm).
Therefore, we have to convert the lengths in the units of metres.
The relation between centimetre and metre is that $1cm={{10}^{-2}}m$.
Therefore, we get that $1c{{m}^{2}}={{10}^{-4}}{{m}^{2}}$.
Substitute the value of 1$c{{m}^{2}}$ in equation (i).
This gives us that A =$1000\left( {{10}^{-4}}{{m}^{2}} \right)=0.1{{m}^{2}}$.
Therefore, the area of the board in the MKS unit is 0.1${{m}^{2}}$.

Note:
The unit centimetre belongs to the CGS system of units. The full form of CGS is centimetre gram second. In this system, centimetre is a unit of length, gram is a unit of mass and second is a unit of time.
The full form of MKS is metre kilogram second. In this system, metre is a unit of length, kilogram is a unit of mass and second is a unit of time.