Question

Wire of resistance 5 ohm is uniformly stretched untill new length becomes 4 times the original length.find it's resistance?

Answer 1

$r = raw \: l \div a$
$rn = raw \: ln \: \div an$
$rn = 4l \div 1 \div 16a \: raw$
$rn = 1 \div 4r$

$ln = 4l$
$an = 1 \div 4a$