Thinking / Planning
Noting that Sarah spent all
her money in both scenarios and that 22´(18´something) = 18´(22´something) , I am going to first guess that Sarah takes 18 days and 22 days to spend all her money
in the 1st scenario and the 2nd scenario respectively. [ Heuristics:
H07. Use guess and check & H08. Make suppositions ] Then I try to adjust my educated guess.
Johari spent more money in the second scenario. The difference in his spending
among the two cases is 6, so we need
10´(number of days2)
– 12´(number of days1)
= 6
Solution
If Sarah takes 18 days and 22 days respectively to spend
all her money, then
the difference in
Johari’s spending among the two cases is
10´(22) – 12´(18) =
4
´3/2: 10´(33) – 12´(27) =
6
Ans (a): Sarah has $22´27 = $594.
Ans (b): Johary has $(21+12´27) = $345.
Ans (b): Johary has $(21+12´27) = $345.
Commentary
If the amounts of money involved were in the trillions, we would have thought that Sarah and Johari are certain countries, wouldn't we?
I guess all solutions (even the one above) would have some notion of
“ratio” hidden in it. The reason is:
every time you multiply or divide by something, there is actually a ratio
involved. But I hope this solution is “easy”
enough.
Anyway, a parent from a Facebook parent-support group posed this question asking for a simple solution without using
ratios. This question seems to be the
equivalent of a system of simultaneous equations in four variables. A few of us tried various methods to solve it,
but all were quite complicated. I knew
this can be solved using algebra, but struggled for some time to give a simple
solution.
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