Question

The length of the pipe is 1 km and its diameter is 20 cm.if the diameter of an equivalent pipe is 40 cm. then its length is

Answer 1

$1km = 100000 \: cm \\ volume \: of \: the \: pipe = \pi \times 10 \times 100000 \: cm \: cube \\ let \: for \: the \: new \: pipe \: its \: lengh \: is \: x \: cm \\ according \: to \: the \: question \\ \pi \times 20 \times x = \pi \times 10 \times 100000 \\ or \: x = 1000000 \div 20 \\ or \: \: x = 50000 \: cm\\ or \: \: x = \frac{1}{2} km$