Các bài toán số học trong đề thi APMOPS 2010Posted: September 21, 2013
Question 1: Find the last digit of the number (859435 of 2’s).
Solution: It is easy to prove by induction that the last digit of the number having the form is 8. Hence, the last digit of the number given in the question is 8.
Question 2: Find the value of
Solution: Remember that for any natural number , we always have
Question 3: Find the smallest whole number that is not a factor of
Solution: We just need to consider these five numbers: 24, 25, 26, 27, 28, 29 (29 is a prime number).
Notice that 24=4.6 ; 25=5.5 ; 26=2.13 ; 27=3.9 ; 28=4.7 ; Hence 29 is our result.