the lenght of a minute hand of a wall clock is 7cm.How much area does it sweep in 20 minutes?
Answers
Answered by
47
the length of the minute hand will be the radius of the sector are which it will sweep
so in 60 minutes it sweeps 360°
so in 20 minutes it will sweep 120 °
therefore
by area of sector,
120/360× π(7)²
=π(7)²/3
=154/3 cm²
=51.333 cm²
so in 60 minutes it sweeps 360°
so in 20 minutes it will sweep 120 °
therefore
by area of sector,
120/360× π(7)²
=π(7)²/3
=154/3 cm²
=51.333 cm²
Answered by
23
we know
60 minutes =1 revolution by minute hand
so, 1 minute=1/60 revolution
20 minutes=1/60 x 20=1/3 revolution
we also know ,
1 revolution = 1 circle area
1/3 revolution=1/3 circle area
hence area formed in 20 minutes by minute hand =1/3pi.r^2
=1/3 x 22/7 x 7 x 7=154/3 cm^2
60 minutes =1 revolution by minute hand
so, 1 minute=1/60 revolution
20 minutes=1/60 x 20=1/3 revolution
we also know ,
1 revolution = 1 circle area
1/3 revolution=1/3 circle area
hence area formed in 20 minutes by minute hand =1/3pi.r^2
=1/3 x 22/7 x 7 x 7=154/3 cm^2
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