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Rob is a high school student taking both algebra and geometry. last night he had 27 homework problems combined from the two classes, and he took a total of 90 minutes to do them. if each algebra problem took him 2 minutes and each geometry problem took him 5 minutes, how many algebra problems did he have for homework

Sagot :

Let the number of algebra problems be x

Let the number of geometry problems be y

Total problems = 27

Total time = 90 minutes

Time for one algebra problem = 2 minutes

Time for one geometry problem = 5 minutes

Hence,

x + y = 27

→ x = 27 – y

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[tex]2x + 5y = 90[/tex]

[tex]2(27 - y) + 5y = 90[/tex]

[tex]2(27) - 2y + 5y = 90[/tex]

[tex]3y = 90 - 54[/tex]

[tex]3y = 36[/tex]

[tex]y = \frac{36}{3} [/tex]

[tex]y = 12[/tex]

[tex]x = 27 - 12 = 15[/tex]

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Answer:

→ He had 15 algebra problems for the homework