Hi
I'm posting this on behalf of my aunt's friend's son who is
currently in primary one and the he has come up with a problem sum
that he cannot solve at all. In desperation, my aunt asked me to
try to help him with one problem sum that even an O Level graduate
like me couldn't solve it without using algebra. Is there anyone
willing to help this boy? Thanks in advance.
Here goes the question:
Kim, Mei and Yanti collect stamps. Kim and Mei have 220 stamps
more than Yanti. Yanti and Mei have 140 stamps more than Kim. Kim
and Yanti have 500 stamps. How many stamps does Mei have?
My answer is 180, using System of Linear Equations
Silly Singapore PSLE Math that force you not to use algebra.
Whatever works most efficiently is by definition the best method.
This is why I teach A levels, not PSLE. So, while I can't help you
out with a non-algebra method, this confirms your final answer is
correct.
K + M = 220 + Y
Y + M = 140 + K
K + Y = 500
Sub K = (500 - Y) into 1st eqn, we get : 2Y - M = 280, hence M =
2Y - 280
Sub K = (500 - Y) and M = (2Y - 280) into 2nd eqn, we get : Y +
(2Y - 280) = 140 + (500 - Y), hence 4Y = 920, ie. Y = 230
Concordantly, K = 270, and M = 180.
