Answer :
Number of boys are 30
Assume number of boys (X) , Number of Girls (Y)
X + Y = 70 (1)
X/Y = 3/4
Y = 4/3X (2)
replacing the value of Y in (2) in number (1)
X + 4X/3 = 70
7X/3 = 70
7X = 210
X = 30
so number of boys = 30 boys
Assume number of boys (X) , Number of Girls (Y)
X + Y = 70 (1)
X/Y = 3/4
Y = 4/3X (2)
replacing the value of Y in (2) in number (1)
X + 4X/3 = 70
7X/3 = 70
7X = 210
X = 30
so number of boys = 30 boys