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5 votes
For how many different pairs of positive integers (a,b) with greatest common factor 1, and with a>b, does ab=30!

User Fasfsfgs
by
6.7k points

1 Answer

5 votes

Answer:

4 pairs

Explanation:

Given

ab = 30

Where

a > b

Required

Determine number of pairs (a,b)

To do this, we simply test values for a and b that satisfy the required condition.

First,

Take a = 30

Substitute 30 for a in ab = 30

30 * b = 30

b = 30/30

b = 1

The pair is (30,1)

Take a = 15

Substitute 15 for a in ab = 30

15 * b = 30

b = 30/15

b = 2

The pair is (15,2)

Take a = 10

Substitute 10 for a in ab = 30

10 * b = 30

b = 30/10

b = 3

The pair is (10,3)

Take a = 6

Substitute 6 for a in ab = 30

6 * b = 30

b = 30/6

b = 5

The pair is (6,5)

There exist no other pair that satisfy the given condition.

Counting the above pairs, there are just 4 pairs.

User MayeulC
by
6.9k points
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