Question

a number is more than its 40 % by 510 find the number

Answer 1

let the number be x.
40% of x=40x/100

Now by condition,
x=40x/100 +510
x=4x/10 +510
x=(4x+5100)/10
10x=4x+5100
6x=5100
x=5100/6
x=850

I hope it helps.

Answer 2

let the no. be x.
then,
x- (40% of x )=510
=> x- (40x/100) =510
=> x- (2x/5) =510
=> 3x/5 = 510
=> 3x = 2550
=> x = 850

hence the ans is 850