Question 505639
What is your average velocity if you drive a distance of 464 km at a speed of 48 km/h, then the same distance at a speed of 68 km/h? Answer in units of km/h.
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Let a = the average velocity
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Write a time equation, time = dist/speed
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{{{464/48}}} + {{{464/68}}} = {{{2(464)/a}}}
{{{464/48}}} + {{{464/68}}} = {{{928/a}}}
Find the LCM of 48 and 68
48: 2*2*2*2*3
68: 2*2*17
LCM 2^4 * 3 * 17 = 816
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Multiply by 272a
816a*{{{464/48}}} + 816a*{{{464/68}}} = 816a*{{{928/a}}}
Cancel the denominators and you have
17a(464) + 12a(464) = 816(928)
7888a + 5568a = 757248
13456a = 757248
a = {{{757248/13456}}}
a = 56.276 km/hr is the average velocity for the trip
:
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You can confirm this by finding if the actual times add up
{{{464/48}}} + {{{464/68}}} = {{{928/56.276}}}