ABACUS International Math Challenge
for
3rd and 4th graders
October, 2008
A.649. How many 3-digit numbers have exactly
one digit 5?
A.650. Five girls and three boys want to
play soccer. How many different ways can they make two teams of 4 players
if each team must have at least one boy?
A.651. Make as many 3-digit numbers as
you can using the digits 5, 6, and 7 exactly once in each number. What is
the sum of all those numbers?
A.652. We painted a 10 cm x 10 cm x 10
cm cube red. Then we cut it up into 1 cm x 1cm x 1cm little cubes by cuts
parallel to the sides of the big cube. How many of the little cubes have
red paint on them?
A.653. Is it true that you can always find
two numbers among six odd numbers whose difference is divisible by 10?
A.654. Is it true that you can always find
two numbers among 4 odd numbers whose difference or sum is divisible by
10?
A.655. How many square numbers are there
from 1 to 2008?
A.656. In some of the 3-digit numbers every
digit is less than 4. How many such numbers are there?
Please, send your solutions to:
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