The usual price of a notebook sold at Shop P and Q is $28. During a sale, a discount of 25% is given to every notebook sold at Shop P. At Shop Q, a discount of 50% is given to the 4th notebook for every 4 notebooks sold. How much cheaper would it be if Min buys 10 notebooks from Shop P instead of Shop Q?

	Shop P	Shop Q
Price of 1 notebook	75%  $21	100% $28
Every 4th notebook		50% $14

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

Price of 1 notebook from Shop P at 25% discount
= 75% x 28
= ⁷⁵₁₀₀ x 28 
= $21

Cost of 10 notebooks from Shop P
= 10 x 21
= $210

Price of the 4th notebook from Shop Q in percentage
= 100% - 50%
= 50%

Cost of 4th notebook at Shop Q
= 50% x 28
= ⁵⁰₁₀₀ x 28 
= $14

Cost of 1 set of 4 notebooks at Shop Q
= 28 x 3 + 14
= $98

Number of sets of 4 for notebooks at Shop Q
= 10 ÷ 4
= 2 r 2

Cost of 2 sets of 4 notebooks at Shop Q
= 2 x 98
= $196

Cost of 2 notebooks at Shop Q
= 2 x 14
= $28

Cost of 10 notebooks at Shop Q
= 196 + 28
= $224

Amount cheaper if Min buys 10 notebooks from Shop P instead of Shop Q
= 224 - 210
= $14

Answer(s): $14