We have,
Long side of rectangular field is 60 meters more then the shorter side.
Let the longer side will be (y+30)mtr.
And the length of the diagonal will be (y+60) mtr.
Now, According to given question.
Using Pythagoras theorem,
(Diagonal)2=(shorterside)2+(longerside)2
(y+60)2=y2+(y+30)2
⇒y2+3600+120y=y2+y2+900+60y
⇒3600+120y−y2−900−60y=0
⇒−y2+60y+2700=0
⇒y2−60y−2700=0
⇒y2−(90−30)y−2700=0
⇒y2−90y+30y−2700=0
⇒y(y−90)+30(y−90)=0
⇒(y−90)(y+30)=0
If,
y+30=0
y=−30(notpossible)
If,
y−90=0
y=90
So, the length of shorter side =y−30=90−39=60
Longer side 90+30=120
Hence, this is the answer.