local brainteaser

[loopy lass]

In a sack race at a school sports day Ben finished in seven-eighths of the time Tristan took, minus 20 seconds. Daniel finished in two-thirds plus ten seconds of Tristan's time. If Ben and Daniel finished at the same time, how long did Tristan take.
thanks in advance, this is the last one to do and am guessing it is a stupid answer but just can't see it.

[smouse]

72 seconds

[mohill]

Tristan took 144sec
Seven-eighths of this is 126; 126 minus 20 is 106
Two-thirds of this is 96; 96 plus 10 is 106
Cheers

[loopy lass]

was there a logical way to work it out, or are you guessing cos i've used your 72 secs and tried to work it backwards and Ben and Daniel don't have the same time, can you explain? thanks

[loopy lass]

thanks mohill that one works.

[smouse]

sorry bad maths on my part I had just got up is my excuse
I read 2/3rd as one 1/3
Ben = 7/8T -20
Daniel = 2/3T + 10
as ben = daniel
7/8T - 20 = 2/3 T = 10

[mohill]

Hi loopy lass. I used the equation that smouse shows on his last line, ie 7/8T - 20 = 2/3T + 10
You probably remember how to solve it but in case you don't, here are the steps:
7/8T - 20 = 2/3T + 10
(Multiply right through by 24 to clear the fractions)
21T - 480 = 16T + 240
(Add 480 to each side)
21T = 16T + 720
(Subtract 16T from each side)
5T = 720
(Divide both sides by 5)
T = 144
I hope this is not patronising.
Cheers

[loopy lass]

thanks mohill, it's not patronising at all. sometimes you need to see something the easy way to make it sink in.
smouse, don't apologise, my brain doesn't function first thing in the morning either.
Thanks to both of you for bothering to help.