Question -
Answer -
Let R and r be theradii of the top and base of the bucket respectively,
Let h be its height.
Then, we have R = 20cm, r = 10 cm, h = 30 cm
Capacity of the bucket= Volume of the frustum of the cone
= 1/3 ╧А(R2┬а+r2┬а+ R r┬а)h
= 1/3 ╧А(202┬а+102┬а+ 20 x 10┬а) x 30
= 3.14 x 10 (400 + 100+ 200)
= 21980 cm3┬а=21.98 litres
Now,
Surface area of thebucket = CSA of the bucket + Surface area of the bottom
= ╧А l (R + r) + ╧Аr2
We know that,
l = тИЪh2┬а+(R тАУ r)2
= тИЪ[302┬а+(20 тАУ 10)2] = тИЪ(900 + 100)
= тИЪ1000 = 31.62 cm
So,
The Surface area ofthe bucket = (3.14) x 31.62 x (20 + 10) + (3.14) x 102
= 2978.60 + 314
= 3292.60 cm2
Next, given that thecost of 1 litre milk = Rs 25
Thus, the cost of21.98 litres of milk = Rs (25 x 21.98) = Rs 549.50