UPSC CDS 2 2021 Math Paper

Given, Dimensions of cylinder 1 :
Radius (r1)=7cm
Height (h1)=20cm
Dimensions of cylinder 2 :
Radius (r2)=3.5cm
Height (h2)=10cm Volume of the solid rod = Volume of cylinder 1+ Volume of cylinder 2 .
‌‌=πr12h1+πr22h2
‌‌=‌

22

7

×(7×7×20+3.5×3.5×10)
‌‌=‌

22

7

(7×140+3.5×35)
‌‌=22(140+3.5×5)
‌‌=22(140+17.5)
‌‌=22(157.5)=3465cm3
‌‌=‌

3465

100×100×100

m3
∴‌ Mass of rod ‌
‌‌=‌

3465

100×100×100

×10000kg
‌‌=34.65kg
Hence, mass of the rod is 34.65kg.