Tag Archives: modulo arithmetic

Divided by 5

Find the reminder when is divided by ? Source: NCTM Mathematics Teacher, October 2006 Solution is such a large number that it is impractical to use modulo arithmetic to find the remainder. So we are going to find the remainders … Continue reading

Posted in Problem solving | Tagged , , , , | Leave a comment

Divisible by 7

How many four digit positive integers divisible by have the property that, when the first and last digits are interchanged, the result is a (not necessarily four-digit) positive integer divisible by ? Source: NCTM Mathematics Teacher, October 2006 Solution Is … Continue reading

Posted in Problem solving | Tagged , , , , , , , , | Leave a comment

Pairs of Digits

How many pairs of decimal digits exist with the property that if is an integer ending in those two digits, then ends in the same two digits? Repetition of the digits in a pair is allowed. Source: NCTM Mathematics Teacher, … Continue reading

Posted in Problem solving | Tagged , , , , , | Leave a comment

Sum of Powers of Five

Compute the units digit of . Source: NCTM Mathematics Teacher 2008 SOLUTION 1 The units digits of follows the following pattern. If , the units digits of the sum are . For example, , units digit = , units digit … Continue reading

Posted in Problem solving | Tagged , , , , , | Leave a comment

Divisibility of Pythagorean Triples

1. Show that if are integers such that , then (a) at least one of them is divisible by (b) at least one of them is divisible by (c) at least one of them is divisible by . 2. Show … Continue reading

Posted in Problem solving | Tagged , , , , , , | Leave a comment

Hill Cipher

I. Consider the following equation where and represent two relatively prime integers (a) Verify that the ordered pair is a solution of Eq. (b) Use part (a) to find a parametric solution of Eq. (c) Derive an integer such that … Continue reading

Posted in Problem solving | Tagged , , , , , | Leave a comment

No Integer Solutions

1. Show that the following system of equations has no integer solutions 2. Show that the following system of equations has no integer solutions Source: http://www.math.rutgers.edu/~erowland/modulararithmetic.html SOLUTION 1. We reduce the equations and hope to find a contradiction thereby showing … Continue reading

Posted in Problem solving | Tagged , , , | 1 Comment