To solve this problem, we need to examine the conditions given for the pairs (a,b) of positive integers:
1. The greatest common divisor (GCD) of a and b is 1⋅2⋅3⋅…⋅50.
2. The least common multiple (LCM) of a and b is 12⋅22⋅32⋅…⋅502.
### Step 1: Express Conditions Using Prime Factorization
First, let's write both the GCD and LCM conditions using prime factorization.
Let P=1⋅2⋅3⋅…⋅50.
The prime factorization of P would be:
P=2p2⋅3p3⋅5p5⋅…⋅47p47
where pk is the power of the prime k in the factorization of the numbers from 1 to 50.
The LCM condition translates to:
LCM(a,b)=12⋅22⋅32⋅…⋅502=22p2⋅32p3⋅52p5⋅…⋅472p47
### Step 2: Relate GCD and LCM to (a,b)
For (a,b), we have:
- a=2a2⋅3a3⋅…⋅47a47
- b=2b2⋅3b3⋅…⋅47b47
For each prime k:
GCD(a,b)=kmin(ak,bk)=kpk
LCM(a,b)=kmax(ak,bk)=k2pk
Thus, we have:
- min(ak,bk)=pk
- max(ak,bk)=2pk
### Step 3: Determine the Number of Solutions for Each Prime
For each prime k:
- If ak=pk, then bk can be any integer such that bk≥pk and bk≤2pk.
- Similarly, if bk=pk, ak can be any integer such that ak≥pk and ak≤2pk.
This provides two options for each prime k:
1. (ak,bk)=(pk,2pk)
2. (ak,bk)=(2pk,pk)
Since each prime can independently take one of these configurations, we have 2 choices per prime. Given there are 15 prime numbers from 1 to 50 (including repeated primes in products like 24, 33, etc.), the total number of pairs (a,b) is:
215=32768
Thus, the number of pairs (a,b) satisfying the given conditions is:
32768