Find the radii of circles whose areas are1 1-386 cm 22 15-400 sq- cm

(1) A = πr2 i.e. 1386 = × r2 i.e. × r2 = 1386 r2 = 1386 × r2 = 441 = 212 ∴ r = 21 cm (2) A = πr2 i.e. 15400 = × r2 i.e. × r2 = 15400 r2 = 15400 × r ...

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Byju's Answer

Standard VII

Mathematics

Area of Circle

Find the radi...

Question

Find the radii of circles whose areas are

(1) 1.386 cm²

(2) 15,400 sq. cm

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Solution

(1) A = πr²

i.e. 1386 = × r²

i.e. × r²= 1386

r²= 1386 ×

r²= 441 = 21²

∴ r = 21 cm

(2) A = πr²

i.e. 15400 = × r²

i.e. × r² = 15400

r²= 15400 ×

r²= 4900 = 70²

∴ r = 70 cm

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Find the radii of circles whose areas are (1) 1.386 cm2 (2) 15,400 sq. cm

(1) A = πr2 i.e. 1386 = × r2 i.e. × r2 = 1386 r2 = 1386 × r2 = 441 = 212 ∴ r = 21 cm (2) A = πr2 i.e. 15400 = × r2 i.e. × r2 = 15400 r2 = 15400 × r2 = 4900 = 702 ∴ r = 70 cm

Find the radii of circles whose areas are

(1) 1.386 cm²

(2) 15,400 sq. cm

(1) A = πr²

i.e. 1386 = × r²

i.e. × r²= 1386

r²= 1386 ×

r²= 441 = 21²

∴ r = 21 cm

(2) A = πr²

i.e. 15400 = × r²

i.e. × r² = 15400

r²= 15400 ×

r²= 4900 = 70²

∴ r = 70 cm