The usual price of a notebook sold at Shop D and E is $10. During a sale, a discount of 20% is given to every notebook sold at Shop D. At Shop E, a discount of 40% is given to the 4th notebook for every 4 notebooks sold. How much cheaper would it be if Emma buys 11 notebooks from Shop D instead of Shop E?

	Shop D	Shop E
Price of 1 notebook	80%  $8	100% $10
Every 4th notebook		60% $6

Price of 1 notebook from Shop D in percentage
= 100% - 20%
= 80%

Price of 1 notebook from Shop D at 20% discount
= 80% x 10
= ⁸⁰₁₀₀ x 10 
= $8

Cost of 11 notebooks from Shop D
= 11 x 8
= $88

Price of the 4th notebook from Shop E in percentage
= 100% - 40%
= 60%

Cost of 4th notebook at Shop E
= 60% x 10
= ⁶⁰₁₀₀ x 10 
= $6

Cost of 1 set of 4 notebooks at Shop E
= 10 x 3 + 6
= $36

Number of sets of 4 for notebooks at Shop E
= 11 ÷ 4
= 2 r 3

Cost of 2 sets of 4 notebooks at Shop E
= 2 x 36
= $72

Cost of 3 notebooks at Shop E
= 3 x 6
= $18

Cost of 11 notebooks at Shop E
= 72 + 18
= $90

Amount cheaper if Emma buys 11 notebooks from Shop D instead of Shop E
= 90 - 88
= $2

Answer(s): $2