MATHEMATICS WITHOUT BORDERS 2015-2016 AUTUMN 2015: GROUP 2 ...

MATHEMATICS WITHOUT BORDERS 2015-2016

AUTUMN 2015: GROUP 2

Problem 1. What is the missing number?

A) 10

B) 11

Problem 2. The sum of 10 + 8 equals:

C) 21

A) the sum of 6 and 11

B) the difference of 14 and 4 C) the sum of 9 and 9

Problem 3. In a sum of two numbers, one addend is greater than 2 by 2, while the other addend is

smaller than 1 by 2. The sum is:

A) 2

B) 4

C) 5

Problem 4. What is the largest two-digit number with 0 as a units digit?

A) 10

B) 90

C) 100

Problem 5. How many of the following expressions are correct?

11-2 > 13

18+3 > 20

12-5 = 3+4

A) 1

B) 2

C) 3

Problem 6. How many are all the possible digits that can be placed instead of @, so that

would be true?

A) 9

B) 6

C) 3

Problem 7. What is the largest sum of 2 different single-digit numbers?

A) 19

B) 18

C) 17

Problem 8. I thought of a number. I added it to 2 and got 10. The number I thought of is:

A) 12

B) 8

C) 10

Problem 9. One of the addends is the smallest two-digit number, and is larger by 1 than the other

addend. What is the sum of the two addends?

A) 11

B) 19

C) 21

Problem 10. How many are the two-digit numbers that do NOT have 9 as a ones digit?

A) 9

B) 81

C) 90

Problem 11. Peter solved 3 problems, Iva solved 2 problems less than Peter; Mary solved one problem more than Iva. How many problems did Mary solve?

Problem 12. There is a basket in a dark room. In the basket there are 2 yellow and 3 red apples. What is the smallest possible number of apples we would need to take out, without looking at their colour, in order to ensure that we have taken out 2 red apples?

Problem 13. How many single-digits numbers is the magic square made of?

6 8 1 5 2

Problem 14. How many sheets of paper are there between the third and the seventh pages of a book?

Problem 15. Find the sum of all two-digit numbers whose sum of digits is 3?

Problem 16. How many numbers have been omitted in the sequence 1, 11, 21, 31, ..., 81, 91?

Problem 17. Joel has a few bunnies. Each one of them has 2 ears and 4 legs. If their ears are 10 in total, how many legs do they have in total?

Problem 18. If the minuend is 9 and the subtrahend is 9, we get a difference of?

Problem 19. How many units are there in the number equal to

?

?

?

?

? ?

Problem 20. How many sticks with a length of 4 cm can we cut off from a stick with a length of 17 cm?

ANSWERS AND SHORT SOLUTIONS

Problem 1 2 3

4 5 6 7 8 9 10

Answer B C C

B B C C B B B

Solution

10 + 8 = 18, 18 = 9 + 9

2 + 2 = 4; 2 ? 1 = 1

4 + 1 = 5

90

9>13; 21>20; 7=7

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