PSC, RRB, SSC, ADRE, Banking, and Other Competitive Exams

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Q. A garden is 21 meters long and 15 meters wide. There is a path 2 meters wide all around it. Grass is planted on the path at the rate of 2.75 taka per square meter. Find the total cost.

Solⁿ:

Garden length = 21 m
Garden width = 15 m
Garden area = 21×15 = 315 sq.m

Path is 2 m wide on all sides.

So, total length including path = 21+ 2 + 2 = 25 m
Total width including path = 15 + 2 + 2 = 19 m

Total area including path = 25×19 = 475 sq.m

Area of path = Total area - Garden area

                     = 475 - 315 = 160 sq.m

Cost of grass per sq.m = Rs 2.75
Total cost = 160 × 2.75 = Rs 440

Ans: Rs440

Q. A cylinder has a total surface area of 396 cm² and a radius of 7 cm. Find the volume of the cylinder (in cm³).  Use π=22/7

Soln:

Find the height h

TSA = 2πr(r+h)

2*22/7*7*(7+h) = 396

44(7+h) = 396  ⟹  7+h = 9  ⟹  h = 2 cm

Find the Volume V

V = πr^2h = 22/7*7^2*2 = 308 cm³

Ans: 308 cm³