Question

QNO 8 - Making a model
Pawan, a student of class 9th, was asked to make a science model shaped like a cylinder with
open base and conical above it by using a cardboard sheet. The diameter of the model is 21 cm
and its length is 28 cm. The height of the cylinder is 20 cm.
(a) Find the curved surface area of the cylindrical portion.
(1)1250 cm² (ii)1320 cm2 (iii)1300cm? (iv)1200 cm?
(b)Find the slant height of the conical portion.
(0) 697/2 cm (ii)26cm (iii) V 630/2cm (iv)24cm
(c) Write the formula to find the lateral surface area of conical portion.
( (i) a rh
(ii) 2nrh + tr 2 (iii) or (iv)nr 2 h
(d) How much is the volume of a cylinder if the radius and height of the base is 7 cm and
14cm?
(i) 2056cm2
(ii)2156cm2 (iii)2516cm2 (iv)2650cm?
(e) write the formula to find the area of the cardboard sheet used to make the model.
(i)trh + nrl (ii) 2nrh + ar (iii)2tr + Tr? (iv) 2 trh + terl​

Answer 1

Answer:

a.  1320 cm2

b. √630/2cm

c.  πrl

d.2156cm2