Question

A circular mirror of radius 21 cm is surrounded by a circular frame of width 3.5.Find the cost of making the frame at ₹1.50 per cm²

Answer 1

Answer:

₹ 750.75

Step-by-step explanation:

r = 21 cm

Width = 3.5 cm

π = $\frac{22}{7}$

Area of the Circular ring  = π$R^{2}$ = $\frac{22}{7} * 21 * 21 = 1386 cm^{2}$

Area of Circle with Frame = π$r^{2}$ where r = 21 cm + 3.5 cm = 24.5 cm

= $\frac{22}{7} * 24.5 * 24.5 = 1886.5cm^{2}$

∴ Area of the Frame = $1886.5cm^{2} - 1386cm^{2} = 500.5cm^{2}$

Rate of making frame = ₹ 1.5 per $cm^{2}$

∴Price of Making Frame = ₹ $(500.5 * 1.5)$ = ₹ 750.75

Answer 2

Step-by-step explanation:

Answer:

₹ 750.75

Step-by-step explanation:

r = 21 cm

Width = 3.5 cm

π = \frac{22}{7}

7

22

Area of the Circular ring = πR^{2}R

2

= \frac{22}{7} * 21 * 21 = 1386 cm^{2}

7

22

∗21∗21=1386cm

2

Area of Circle with Frame = πr^{2}r

2

where r = 21 cm + 3.5 cm = 24.5 cm

= \frac{22}{7} * 24.5 * 24.5 = 1886.5cm^{2}

7

22

∗24.5∗24.5=1886.5cm

2

∴ Area of the Frame = 1886.5cm^{2} - 1386cm^{2} = 500.5cm^{2}1886.5cm

2

−1386cm

2

=500.5cm

2

Rate of making frame = ₹ 1.5 per cm^{2}cm

2

∴Price of Making Frame = ₹ (500.5 * 1.5)(500.5∗1.5) = ₹ 750.75