Please help me this word problem Kevin drove 320 miles to a

Please help me this word problem: Kevin drove 320 miles to a mountain resort. His return trip took 20 minutes longer because his speed returning was 4 mi/h slower than his speed going.

Solution

(1) T1 = 320 / V1
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(2) T2 = 320 / V2,,,,,but T2 = T1 + 20/60 (hrs) ,,,and V2 = V1 -4
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subst in (2)
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{ T1 + 20/60} = 320 / {V1-4},,,and T1 = 320 /V!
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{ (320/V1) +20/60 } = 320 /{V1-4)
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Multiply thru by (3) V1(V1-4)
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(320 (3) (V1-4) + 1(V1)(V1-4) = 320 (3)(V1)
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960 V1 - 3840 + V1^2 -4V1 = 960V1
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v1^2 -4V1 -3840 =0,,,,,factor
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(V1 -64)(V1+60) =0
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V1= 64, -60 ( not practical)
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check,,,V1= 64,,,V2 = 60
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T1 = 320 /64 = 5 hrs
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T2 = 5 hrs + 1/3 hr = 5.33 hrs
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T2 = 320 / 60 = 5.333