Respuesta :

kitamuragu
As Jack can mow the yard 7/3 Times faster than Marilyn , Jack can mow 70% of the yard while Marilyn can mow 30% of the yard in the same time Jack would mow 70%.

Jack can mow 10% of the yard in 0.3 hours
Marilyn can mow 10% of the yard in 0.7 hours

Jack will mow 70% of the yard : 0.3 hours ( 10% ) × 7
= 2.1 hours . Jack can mow 70% of the yard in 2.1 hours

Marilyn will mow 30% of the yard : 0.7 hours ( 10%) × 3 = 2.1 hours. Marilyn can mow 30% of the yard in 2.1 hours.

John mowwing for 2.1 hours + Marilyn mowwing for 2.1 hours = 100% of the yard in 4.2 hours.

Awnser : 4.2 hours

chrysanthemum
Hello!

First, figure out their mowing rates per hour.

Jack's is [tex] \frac{1}{3} [/tex] since he mows 1 lawn in 3 hours; Marilyn's is [tex] \frac{1}{7} [/tex] since she mows 1 lawn in 7 hours.

We now know that their combined rate of mowing 1 lawn is [tex] \frac{1}{3} + \frac{1}{7} [/tex]. Use the variable t for time and multiply it by their combined rate to figure out their combined time of mowing 1 lawn.

[tex]( \frac{1}{3} + \frac{1}{7})t =1[/tex]

[tex]( \frac{7}{21} + \frac{3}{21} )t=1[/tex]

[tex] \frac{10}{21} t =1[/tex]

[tex]t= \frac{21}{10} [/tex]

Answer:
Jack and Marilyn could mow the lawn in [tex] \frac{21}{10} [/tex] or 2.1 hours if they work together.

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