Page 188 - Maths Skills - 8

186 Maths

(b) Both A and R are true but R is not the correct 2. If the length, breadth and height of a cuboid
explanation of A. are 48 cm, 24 cm and 12 cm respectively, find
(c) A is true but R is false. the side of a cube whose volume is equal to the
volume of a cuboid.
(d) A is false but R is true. 3. A classroom is 8 m long, 7 m broad and 4.5 m

Q. 1. Assertion (A): If two right circular cylinders of high. Doors and windows occupy an area of 18
equal volume have their heights in the ratio of m . Find the cost of whitewashing the walls at
2
1:2, then the ratio of their radii is 21: . the rate of ` 2.50 per sq. m.
Reason (R): The height and radius of a cylinder 4. The length, breadth and height of a room are 8.5
are inversely proportional. m, 7 m and 6.5 m respectively. Find the area of
Q. 2. Assertion (A): The area of a triangle can be the four walls of the room. Hence, find the cost
expressed as one-half of the product of its base of whitewashing the walls of the room and its
and height. ceiling at the rate of ` 8 per square metre.
Reason (R): The height of a triangle is the 5. How many cubic metres of earth must be dug
perpendicular distance from its base to its out to sink a well which is 8 m deep and has a
opposite vertex. diameter of 28 m? If the earth taken out is spread
over a rectangular plot 22 m by 16 m, what is the
height of the platform so formed?

SUBJECTIVE TYPE QUESTIONS 6. A roller of diameter 84 cm having length 120
F. Solve the following word problems cm takes 1000 complete revolutions to cover a
playground field. Find the area of the field in m .
2
1. A swimming pool is 250 m long and 150 m
wide. If 9375 m of water is pumped into it, find
3
the height of the water level.

HOTS

1. The diameter of a coin is 1 cm. If four of these coins be placed on a table so that
the rim of each touches that of the other two, find the area of the unoccupied space
between them. (Take π = 3.14)

2. A circular wire of radius 42 cm is cut and bent in the form of a rectangle whose sides are in the ratio of
6 : 5. Find the smaller side of the rectangle.

Word Stock

Area Volume Altitude Diagonal Lateral Surface Perimeter Perpendicular