Calculated standard deviation by shortcut method .

Explanation

Assumed mean = 50
`sigma = isqrt((sumfx^(2))/(N) - ((sum fx')/(N))^(2)) = 20 sqrt((147)/(100) - ((5)/(100))^(2)) = 20 sqrt(1*47 - *0025)`
`20sqrt(1*4675) = 20 xx 1*211 = 24*23` marks