Answer:
Height=28
Step-by-step explanation:
You have to work backwards using the formula for a triangle, A=1/2bh
Plug your values in, 126=1/2 9 h
126=4.5 h
126 divided by 4.5 is 28
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We know that
l² = r² + h²
l² = (10.5)² + (36)²
l² = 110.25 + 1296
l² = 1406.5
l = √(1406.5)
l = 37.5 cm
Now,
CSA of cone = πrl
=> 22/7 × 10.5 × 37.5
=> 22 × 1.5 × 37.5
=> 1237.5 cm²
Area of 20 caps = 20 × 1237.5
=> 24750 cm²
