the external diameters of a hollow hemispherical vessel are 16cm and 12cm respectively. The cost of painting 1cm^2 is Rs.2 . FInd the cost of painting the vessel all over. ans-Rs.1433.14
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given,
internal diameter=12 cm
external diameter =16cm
radius of internal =12/2=6cm
radius of external=16/2=8cm
surface area(internal)=2πr²=2×22/7 ×6×6=2×22×6×6/7=227cm²
surface area (external)=2πR²=2×22/7 ×8×8
=2×22×8×8/7=403cm²
cost of painting = cost of internal+ cost of external+cost of the ring= 2(227)+2(403)+2(π(R²-r²)
=454+806+2(22/7(8²-6²)
=1260+44/7(64-36)
=1260+44/7(28)
=1260+44×4
=1260+176=1436 approx
because the answer come 1436 I take the next number. so it came. if u can use this process. if u want the exact value.
internal diameter=12 cm
external diameter =16cm
radius of internal =12/2=6cm
radius of external=16/2=8cm
surface area(internal)=2πr²=2×22/7 ×6×6=2×22×6×6/7=227cm²
surface area (external)=2πR²=2×22/7 ×8×8
=2×22×8×8/7=403cm²
cost of painting = cost of internal+ cost of external+cost of the ring= 2(227)+2(403)+2(π(R²-r²)
=454+806+2(22/7(8²-6²)
=1260+44/7(64-36)
=1260+44/7(28)
=1260+44×4
=1260+176=1436 approx
because the answer come 1436 I take the next number. so it came. if u can use this process. if u want the exact value.
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