I happened to have a bit time so I posted on your thread.
I work in a small main contractor company. I need to act as an architect, draghtsman, acountant, admin and secretary. My boss is a funny businessman and he was a principle of a primary school before he retired. This old guy asked the client poison the tree before submission.'cause they need to cut the tree. They are too cruel to those workers. They fired a worker and bought him a flight ticket of this early morning(about 7am)yesterday and the guy cried at the airport.
But they are nice to me. I only have one month comformation and a colleage dives us to a nearer subway station everyday.
Yeah. It's because I'm old and I think too much about other things. I only give my daughter hints when I teach her maths. That's the reason why I'm weak on mental calculation. I think I'd better do some maths to practise my mental caculation. lol
I'm terribly sorry about my mistake. I did it on the newspaper and some numbers overlapped the news. lol. I spent this whole afternoon thinking about it when I was shopping. I checked it again and discovered that I had made a funny mistake. When I did the common denominator, 9x12 was supposed to be 108 but I mentally calculated it as 84.(I think I'd better use the calculater to double check next time. rolleyes )
Since it's the total "round' trip, the distance of upstream equals to the one of downstream. The time which the boat took for upstream is x/9 ans the time which the boat took for downstream is x/12.
Add the time together, you will get a simple fomula: x/9 +x/12 = 7(x is the distance destination from the starting pointand the round trip is 2x)
reduction to a common denominator first. That is
9x/108 + 12x/108 = 7;
21x/108 = 7
then simplify it: 7x/36 = 7
So the distance of the destination from the starting point is 36(pls add the unit here).
Your only mistake is that the anwser is 36, not 72. And only need to list the 2 formulae to the girl: 9a=12b & a=b=7.
I'm afraid not, as of yet. Sorry. We still need the drum mics to get the drums done correctly, and we need to figure out how to get the bass to have the right tone and volume, because one always messes up.