90-Second Test Answers
(1) A bat
and a ball cost $1.10 in total. The bat costs $1 more than
the ball. How much does the ball cost?
Correct answer:
5 cents -- if the bat cost $1.05 and the
ball cost $0.05, the difference is $1.00
(intuitive but wrong answer: 10 cents which is incorrect because
$1.00 minus $0.10 = $0.90)
(2) If it takes five machine
five minutes to make five widgets, how long would it take
100 machines to make 100 widgets?
Correct answer: 5
minutes (intuitive but wrong answer: 100 minutes)
(3) In a lake, there
is a patch of lily pads. Every day, the patch doubles in size.
If it takes 48 days for the patch to cover the entire lake,
how long would it take for the patch to cover half of the
lake?
Correct answer: 47
days (intuitive but wrong answer: 24 days)
***
-Rex M. Jacobsen
Sr. Editor
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