Question 1163274
Lewis ran to the store at 8 km/h and then walked home at 3 km/h. How far was it to the store, if the round trip took 11 hours?
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d = distance to the store.
time going = d/8 hours
time back = d/3 hours
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{{{d/8 + d/3 = 11}}} hours
3d + 8d = 264
11d = 264
d = 24 kms
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Check
24/8 + 24/3 = 3+8 = 11 hours
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I need to learn formulas for distance word problems ---
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That's not a formula, it's how you solve it.
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For a formula, for any round-trip, or trip of 2 equal lengths:
Avg speed = {{{2*r[1]*r[2]/(r[1]+r[2])}}}
Avg speed = 2*8*3/(8+3) = 48/11 km/hr
avg speed*11 = 48 km round trip ---> 24 km each way
Notice that the distance is not relevant to finding the avg speed.
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There are a LOT of formulas.  Too many for anyone to remember them all.
But, this one for average speed is similar to that of parallel resistors and parallel work, so it's not difficult to remember.