PHYSICS [3 Mark Question Answer]

Given,
radius = 28mm
value of π is = 22/7
Area = π * r²
= 22/7*28*28
∴ Area in mm² is = 2464 mm²
whereas, Area in cm is = 22/7*28*28/(10*10) or area in mm²/(10*10)
Area in cm is = 24064 cm²

Given,
Base = 20 cm
Height = 15 cm
Area = 1/2*base*height
Therefore,
Area = 1/2*20*15
= 150 cm²

Given,
Length = 20 km
Breadth = 17 km
Area = length * breadth
Therefore,
Area in km² is = 20*17
Area in km² is = 340km²
∴ in hectares area is = 340*10*10
Area in hectares is = 34000 hectares.

Given,
Lengthy = 450 m
Breadth = 145 m
Therefore, Area in m² is = 450*145
Area in m² is = 65250 m²
∴ in hectares area is = 6250/(100*100)
Area in hectares is = 6.52 hectares.

When we have to make a quick judgement and we do not have any tools to do so, we make estimation. Even we make estimations when we do have tools , because actual measurement may be time consuming.
Example: Suppose you have to drink sweetened milk, and you will add two or more spoons of sugar to it according to your taste. By just estimate the amount of sugar to be added by your sensation of taste. And you need not actually weigh out certain fixed amount of sugar.

For measuring area of regular shape by using graph paper following steps will be carried out:-
At first put the shape on the graph paper.
draw the outline of the shape on graph paper.
Counting the boxes inside the drawn outline.
If the area of one box is ‘A’ unit and there are ‘n’ boxes inside the outline.
Then area of the shape will be = A × n unit.