ABACUS International Math Challenge
for
3rd and 4th graders
November, 1999
A.145. Place parentheses in the following
expression so that its value is zero.
2+2x2-2:2+2x2-2:2+2x2-2
A.146. Place parentheses in the following
expression so that its value is the greatest possible.
3+3x3+3x3+3x3+3
A.147. The sum of two numbers is a 3-digit
number that ends with 27. One of the numbers ends with zero, but if you
delete this digit from this number, you get the other number.
A.148. A 6-liter and an 8-liter container
are full of water. There is an empty 11-liter container you may use also.
There is no scale on any of the containers. How would you measure out 5
liters of water?
A.149. The digits of a 4-digit number are
consecutive numbers in an increasing order. Another 4-digit number contains
the same digits as the previous number, but in a decreasing order. About
the third number we know only that it is made up of the same digits as the
previous two numbers. What are these numbers if their sum is 17967?
A.150. Children are playing a game where
you have to figure out the number one of the groups thought of. They thought
of a whole number between 1 and 300. (1 and 300 are included.) Three children
made the following statements about the secret number:
Anna: The number is between 1 and 100.
Baa: The number is not between 101 and 200.
Cecilia: The number is not between 1 and 100.
But two of these girls admitted quickly that they did not tell the truth.
Between what two numbers should you look for the secret number?
A.151. Along the grid lines, cut up a 5x5
square into 7 different-sized rectangles.
A.152. The following pictures were taken
of a cube in three different positions. How many points are there on the
bottom side of the cube in each position?
Please, send your solutions to: