Question

A ring shape metal plate has an internal radius of 7cm and an external radius of 10.5 cm .if the cost of material is rupees 5 per square centi metre ,find the cost of 25 rings.​

Answer 1

Answer:

Rs. 962.50

Step-by-step explanation:

Area of the ring shape metal plate:

$\pi (R^{2} - r^{2}  )$

Where R is external radius, and r is the internal radius

Therefore,

A = π ((10.5 * 10.5) - (7 * 7))

  = π(110.25-49)

  =(22/7)*61.25

Therefore Cost of the ring plate = (22/7)*61.25/5 = Rs. 38.50

Therefore cost of 25 such rings = 38.50 * 25 = Rs. 962.50

Answer 2

Answer:

962.50

Step-by-step explanation:

Area of plate = (22/7)*61.25

Cost of plate = (22/7)*61.25/5

Cost of 25 plates = (22/7)*61.25*25/5 = 962.50