Problem Solving: If 3+2=7, 5+4=23, 7+6=47 and 9+8=79 to what is 10+9 equal?
A person wants to buy 3 paise and 5 paise stamps costing exactly one rupee. If he buys one, which of the following number of stamps won't allow him to buy 3 paise stamps; 6, 7, 9, 8?