Draw a rectangle ABCD Suppose Sunita is standing at A and her friend is standing at C Now to move shortest distance by sunita she has to travel diagonally Connect A and C Now ADC will be a right angle triangle with angle D as 90 degree Now apply Pythogoras theorem on triangle ADC AD^2+DC^2=AC^2 AD=50 and DC=120 Plug in the values and u will get the answer 70