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प्रश्न
The areas of two concentric circles are 1386 cm2 and 962.5 cm2. The width of the ring is
विकल्प
2.8 cm
3.5 cm
4.2 cm
3.8 cm
उत्तर
3.5 cm
Let r cm and R cm be the radii of two concentric circles.
Thus, we have:
πR2 = 1386
`=> 22/7xx"R"^2 = 1386`
`rArr "R" = (1386xx7/22) "cm"^2`
⇒ R2 = 441 cm2
⇒ R = 21 cm
Also,
πr2 = 962.2
`=> 22/7xx"r"^2 = 962.2`
`⇒ r2 = (962.2 × 7/22) "cm"^2`
`=> "r"^2 = (962.2/10xx7/22)"cm"^2`
`=>"r"^2 =1225/4 "cm"^2`
`=> "r" = 35/2 "cm"`
∴ Width of the ring = (R - r)
`= (21 - 35/2) "cm"`
`= 7/2 "cm"`
= 3.5 cm
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