Question

the radius of the circular ends of a frustum of height 12cm are 15cm and 6cm respectively,what is the lateral surface area and total surface area​

Answer 1

Answer:

Step-by-step explanation:

Given

Diameter to top of bucket = 40 cm

Radius (r1) = 402=20cm

Diameter of bottom part of the bucket = 20 cm

Radius (r2) =302=10cm

Depth of the bucket (h) = 12 cm

Volume of the bucket = Π3(r21+r22+r1r2)h

= Π3(202+102+20×10)12

= 8800cm3

Let ‘L’ be slant height of the bucket

=>L = (r1−r2)2+h2−−−−−−−−−−−−√

=>L = (20−10)2+122−−−−−−−−−−−−−√

=>L = 15.620cm

Total surface area of bucket = Π(r1+r2)×L+Π×r22

= Π(20+10)×15.620+Π×102

= 132061√+22007

= 17.87dm2

Given that cost of tin sheet used for making bucket per dm2 = Rs 1.20

So total cost for 17.87dm2 = 1.20×17.87

= Rs 21.40.

∴

Cost for 17.87dm2 = Rs 21.40