Devi and Siti baked 1200 cookies. Alice and Siti baked 900 cookies. Devi baked 4 times cookies as Alice. how many cookies did Siti sell?
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Question
Answer
ChiefKiasu
Let S be the number of cookies Siti baked.
Let D be the number of cookies Devi baked.
Let A be the number of cookies Alice baked.
(1) D + S = 1200
(2) A + S = 900
(3) D = 4A
Substituting (3) into (1):
4A + S = 1200
=> A = (1200 – S)/4 … (4)
Substituting (4) into (2):
(1200 – S)/4 + S = 900
1200 – S + 4S = 3600
3S = 3600 – 1200 = 2400
S = 800
So Siti baked 800 cookies #
(I don’t know how many she sold 🙂 )
Priskhipo