Question

Cost of 90 envelopes is rs10.50 .how many can I buy for rs10

Answer 1

cost of 90 envelopes = 10.50
Cost of 1 envelope = 10.50/9 = 1.67
cost of 10 envelope = (10×1.67) = 16.7
hence the required cost is 16.7 Rs.

Answer 2

cost of one envelope =x rupees
cost of 90 envelope =10.50
acc. to given condition
x=10.50/90
x=1.67
Cost of 10 envelope=1.67×10=1.67 rupees