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QUESTION

CSAT

Hard

Maths

Prelims 2026

If 10m×1000×n=7525×2532×327510^m \times 1000 \times n = 75^{25} \times 25^{32} \times 32^{75}, where nn is not divisible by 1010, then the value of mm is

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Explanation

To find the value of mm, we need to determine the total power of 1010 present in the prime factorization of the right-hand side (RHS) of the equation.

Step 1: Prime factorize the terms on the RHS

  • 7525=(3×25)25=(3×52)25=325×55075^{25} = (3 \times 25)^{25} = (3 \times 5^2)^{25} = 3^{25} \times 5^{50}
  • 2532=(52)32=56425^{32} = (5^2)^{32} = 5^{64}
  • 3275=(25)75=237532^{75} = (2^5)^{75} = 2^{375}

Step 2: Combine the prime factors Multiplying these together, we get: RHS=325×550×564×2375RHS = 3^{25} \times 5^{50} \times 5^{64} \times 2^{375} RHS=2375×325×5114RHS = 2^{375} \times 3^{25} \times 5^{114}

Step 3: Determine the maximum power of 1010 in the RHS A factor of 1010 is formed by multiplying a 22 and a 55. The number of 1010s we can form is limited by the smaller of their exponents.

  • The power of 22 is 375375.
  • The power of 55 is 114114.

The minimum of these is 114114. Therefore, we can factor out 1011410^{114}: RHS=(2114×5114)×2375114×325RHS = (2^{114} \times 5^{114}) \times 2^{375 - 114} \times 3^{25} RHS=10114×2261×325RHS = 10^{114} \times 2^{261} \times 3^{25}

Step 4: Compare with the left-hand side (LHS) The LHS of the equation is given as: LHS=10m×1000×nLHS = 10^m \times 1000 \times n LHS=10m×103×n=10m+3×nLHS = 10^m \times 10^3 \times n = 10^{m+3} \times n

Equating LHS and RHS: 10m+3×n=10114×(2261×325)10^{m+3} \times n = 10^{114} \times (2^{261} \times 3^{25})

The problem states that nn is not divisible by 1010, which means nn cannot contain both 22 and 55 as prime factors. The remaining term (2261×325)(2^{261} \times 3^{25}) has no factors of 55, so it is indeed not divisible by 1010. This means all the powers of 1010 have been completely factored out into the 1011410^{114} term.

Thus, we can equate the powers of 1010: m+3=114m + 3 = 114 m=1143m = 114 - 3 m=111m = 111

Conclusion: The value of mm is 111111.

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