1 basket is between 9 and 10 minutes .
<u>Step-by-step explanation:</u>
Here we have , John kept track of how many baskets were made in a basketball game. After 4 minutes, 5 baskets were made. We need to find How many baskets were made between 9 and 10 minutes . Let's find out:
In order to calculate baskets between 9 min and 10 min we will find baskets at 10 min and at at 9 min , will subtract than !
Baskets at 10 min :
At 4 min we have 5 baskets so , in 10 min
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Baskets at 9 min :
At 4 min we have 5 baskets so , in 9 min
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⇒ 
⇒ 
So , Baskets between 10 & 9 min is 
, which on rounding off gives 1 . Therefore , 1 basket is between 9 and 10 minutes .
I created this using a graphing calculator website called Desmos! You can use this to further explore slopes and lines and graphing in general :)
Company A : 13 + 30m.....where m = # of mattresses
company B : 15 + 28m.....where m = # of mattresses
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company A : cleaning 4 mattresses : 13 + 30(4) = 13 + 120 = 133
company B: cleaning 4 mattresses : 15 + 28(4) = 15 + 112 = 127
so company B would charge less
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company A : cleaning 7 mattresses : 13 + 30(7) = 223
company B: cleaning 7 mattresses: 15 + 28(7) = 211
so by using company B, u would save : 223 - 211 = $ 12
