Subject: Pythagoras Contest Questions
Date: Wed, 14 Apr 1999 09:46:33 -0600
We have students that are preparing for the Pythagoras Contest which is a nation wide Grade 6 math challenge.
In the preparatory tests we have run into several questions that we can not understand.
Is there anyone who can help us?
My name is Bruce. I am Principal of Lakeview School, Regina. The questions are at the grade 6 level on a challenge contest. I am asking the question for the Grade six students and their teachers.
- If 1 * 9 = 0, 9 * 8 = 72, 2 * 8 = 9, then 9 * 9 = ?
A)81 B)19 C)0 D)61 E)80
- To multiply a number by 25 we can
A) multiply it five times by 5
B) multiply it by 5 and then add 5
C) multiply it by 2 and then by 5
D) multiply it by 2 and then add 5
E) multiply it by 100 and then divide it by 4
Thank you in advance for your assistance.
Judi and Walter
Go to Math Central
The rule for problem 1 seems to be:
Subtract one from the first number, add one to the second number and then multiply, so
When checking whether the proposed procedure gives the
same answer as the traditional one, you really only need
ONE bad answer to eliminate a proposal. So take
a SIMPLE number (e.g. 1) and test each of the proposals:
(A) Is 25x1 equal to 5x5x5x5x5x1? NO
(B) Is 25x1 equal to 5x1+5? NO
(C) Is 25x1 equal to 1x2x5? NO
(D) Is 25x1 equal to 1x2+5? NO
(E) Is 25x1 equal to 1x100/4? YES
Thus only option (E) could possibly be correct. Given it is multiple choice, you are done.
If you really want to 'understand' then look at what the
formula suggests as an alternative and see if you can see
WHY it ALWAYS gives the same answer!
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