The usual price of a stapler sold at Shop R and S is $20. During a sale, a discount of 25% is given to every stapler sold at Shop R. At Shop S, a discount of 30% is given to the 6th stapler for every 6 staplers sold. How much cheaper would it be if Abi buys 15 staplers from Shop R instead of Shop S?

	Shop R	Shop S
Price of 1 stapler	75%  $15	100% $20
Every 6th stapler		70% $14

Price of 1 stapler from Shop R in percentage
= 100% - 25%
= 75%

Price of 1 stapler from Shop R at 25% discount
= 75% x 20
= ⁷⁵₁₀₀ x 20 
= $15

Cost of 15 staplers from Shop R
= 15 x 15
= $225

Price of the 6th stapler from Shop S in percentage
= 100% - 30%
= 70%

Cost of 6th stapler at Shop S
= 70% x 20
= ⁷⁰₁₀₀ x 20 
= $14

Cost of 1 set of 6 staplers at Shop S
= 20 x 5 + 14
= $114

Number of sets of 6 for staplers at Shop S
= 15 ÷ 6
= 2 r 3

Cost of 2 sets of 6 staplers at Shop S
= 2 x 114
= $228

Cost of 3 staplers at Shop S
= 3 x 14
= $42

Cost of 15 staplers at Shop S
= 228 + 42
= $270

Amount cheaper if Abi buys 15 staplers from Shop R instead of Shop S
= 270 - 225
= $45

Answer(s): $45