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August 28th, 2018, 11:54 PM   #1
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what is the B's speed?

A and B start moving towards each other from points X and Y respectively .After they meet on the way, they take 16 seconds and 25 seconds to reach Y and X respectively. If A speed is 1.25 m/sec, what is the B's speed?

I can calculate A's distance after meeting B.

After that, I can't proceed.
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August 29th, 2018, 12:25 AM   #2
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August 29th, 2018, 03:19 AM   #3
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I'll assume A has constant speed a m/s and B has constant speed b m/s.

If A and B meet t seconds after setting out, at = 25b and 16a = bt, so 25b² = abt = 16a².

As a = 1.25 is given, 25b² = 25, and so B has speed 1 m/s.
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August 29th, 2018, 03:51 AM   #4
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Quote:
Originally Posted by skipjack View Post
at = 25b and 16a = bt,
How you got this equation: at = 25b and 16a = bt?
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August 29th, 2018, 04:50 AM   #5
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A moves distance at m from X to where the cars meet, which is also the distance B then moves to reach X, which is 25b m. Hence at = 25b, and 16a = bt is obtained similarly.
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August 29th, 2018, 04:59 AM   #6
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Quote:
Originally Posted by skipjack View Post
A moves distance at m from X to where the cars meet, which is also the distance B then moves to reach X, which is 25b m. Hence at = 25b, and 16a = bt is obtained similarly.
Please draw a diagram for this sentence.
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August 29th, 2018, 01:04 PM   #7
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Let M be the point where A meets B.

A moves from X to M (so XM = at), then B moves from M to X (so MX = 25b).
B moves from Y to M (so YM = bt), then A moves from M to Y (so MY = 16a).

XM = MX implies at = 25b.
YM = MY implies bt = 16a.

I'm not sure how to show movement in a diagram.
You could show XMY as a line, with M a bit nearer to Y than to X.
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August 29th, 2018, 06:43 PM   #8
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Practice with this one:

A and B start moving towards each other from points X and Y respectively .
After they meet, they take 2 hours and 18 hours to reach Y and X respectively.
If A's speed is 15 m/hr, what is the B's speed?


[X]A@15.............90..................>6hr.<-------30--------B@5[Y]

[X]18hr.<---------90-----------B@5;A@15.......30.........>2hr.[Y]
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