Page 203 - Start Up Mathematics_6

Example 15: The area of a rectangular field 50 m long is 250 sq. m. Find the width of the field.

Solution: Area of rectangular field = 250 sq. m
Length of the field = 50 m
Area 250
Width of the field = = = 5 m
Length 50
1
Example 16: What is the cost of tiling a rectangular plot of land km long and 200 m wide at
the rate of ` 9 per hundred sq. m? 2
1
Solution: Length of plot = km = 500 m
2
Breadth of plot = 200 m
Area of plot = Length × Breadth
= 500 m × 200 m = 1,00,000 sq. m
Cost of tiling 100 sq. m = ` 9
9
Cost of tiling 1 sq. m =
100
9
∴ Cost of tiling the plot = × 1,00,000 = ` 9,000
100
Example 17: A tablecloth measures 3 m by 2 m 50 cm. Another tablecloth measures 5 m by
1 m 50 cm. Which rectangular tablecloth costs more if they are made of the same
cloth?
Solution: Length of first tablecloth = 3 m
Breadth of first tablecloth = 2 m 50 cm = 2.5 m

Area of first tablecloth = 3 m × 2.5 m = 7.5 sq. m
Similarly, length of second tablecloth = 5 m
Breadth of second tablecloth = 1 m 50 cm = 1.5 m
Area of second tablecloth = 5 m × 1.5 m = 7.5 sq. m
Since, the two tablecloths have equal area, their costs are same.
Example 18: A floor is 6 m long and 5 m wide. A square carpet of side 4 m is laid on the floor.
Find the area of the floor that is not carpeted.
Solution: Area of the floor = Length × Breadth
= 6 m × 5 m = 30 sq. m
Area of the square carpet = Side × Side
= 4 m × 4 m = 16 sq. m
Area of the floor that is not carpeted = 30 – 16 = 14 sq. m
Example 19: A wall to wall carpeting of a room measuring 8 m by 6 m is to be done. What length
of the carpet is just enough if the roll of the carpet is 3 m wide?
Solution: Length of the room = 8 m
Breadth of the room = 6 m
Area to be carpeted = 8 × 6 = 48 sq. m
Let carpet of length l be sufficient to cover the floor.
Now, area of the carpet = area of the floor
l × 3 = 48 sq. m
l = 16 m

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