The usual price of a notebook sold at Shop K and L is $40. During a sale, a discount of 25% is given to every notebook sold at Shop K. At Shop L, a discount of 30% is given to the 5th notebook for every 5 notebooks sold. How much cheaper would it be if Kimberly buys 13 notebooks from Shop K instead of Shop L?

	Shop K	Shop L
Price of 1 notebook	75%  $30	100% $40
Every 5th notebook		70% $28

Price of 1 notebook from Shop K in percentage
= 100% - 25%
= 75%

Price of 1 notebook from Shop K at 25% discount
= 75% x 40
= ⁷⁵₁₀₀ x 40 
= $30

Cost of 13 notebooks from Shop K
= 13 x 30
= $390

Price of the 5th notebook from Shop L in percentage
= 100% - 30%
= 70%

Cost of 5th notebook at Shop L
= 70% x 40
= ⁷⁰₁₀₀ x 40 
= $28

Cost of 1 set of 5 notebooks at Shop L
= 40 x 4 + 28
= $188

Number of sets of 5 for notebooks at Shop L
= 13 ÷ 5
= 2 r 3

Cost of 2 sets of 5 notebooks at Shop L
= 2 x 188
= $376

Cost of 3 notebooks at Shop L
= 3 x 28
= $84

Cost of 13 notebooks at Shop L
= 376 + 84
= $460

Amount cheaper if Kimberly buys 13 notebooks from Shop K instead of Shop L
= 460 - 390
= $70

Answer(s): $70