CAT 2025 Slot 3 QA Question 10

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CAT 2025 Slot 3QAAlgebra • IndicesModerate
If 1212x×424x+1212^{12x}\times4^{24x+12}×5^{2y} = 8^{4z}×2012x\times20^{12x}×243^{3x-6} , where x,yx , y and zz are natural numbers, then x+y+zx+y+z equals
TITA Answer:
Answer and solution

Answer: 112

The equation given is:
1212x×424x+12×52y=84z×2012x×2433x−612^{12x} \times 4^{24x+12} \times 5^{2y} = 8^{4z} \times 20^{12x} \times 243^{3x-6}
And we need to find x+y+zx + y + z where x,y,andx , y , andz$ are natural numbers. The correct answer is supposed to be 112, so I need to make sure I get there.
First, when dealing with equations involving exponents, it's helpful to express all the bases as powers of prime numbers. That way, I can equate the exponents of the same primes on both sides of the equation. The prime numbers involved here seem to be 2, 3, and 5. Let me rewrite each term accordingly.
Starting with the left-hand side (LHS):
1
1212x12^{12x}: 12 can be written as 22×312^2 \times 3^1. So, 1212x=(22×3)12x=224x×312x12^{12x} = (2^2 \times 3)^{12x} = 2^{24x} \times 3^{12x}.
2
424x+124^{24x+12}: 4 is 22,sothisbecomes2^2 , so this becomes(2^2)^{24x+12} = 2^{48x + 24}$.
3
52y5^{2y} remains as it is because 5 is already a prime.
So, putting it all together, the LHS becomes:
224x×312x×248x+24×52y2^{24x} \times 3^{12x} \times 2^{48x + 24} \times 5^{2y}
I can combine the exponents of the same base on the LHS:
For base 2: 24x+48x+24=72x+2424x + 48x + 24 = 72x + 24
For base 3: 12x12x
For base 5: 2y2y
So, LHS simplifies to:
272x+24×312x×52y2^{72x + 24} \times 3^{12x} \times 5^{2y}
Now, moving on to the right-hand side (RHS):
1
84z8^{4z}: 8 is 23,sothisbecomes2^3 , so this becomes(2^3)^{4z} = 2^{12z}$.
2
2012x20^{12x}: 20 is 22×51,sothisbecomes2^2 \times 5^1 , so this becomes(2^2 × 5)^{12x} = 2^{24x} × 5^{12x}$.
3
2433x−6243^{3x-6}: 243 is 35,sothisbecomes3^5 , so this becomes(3^5)^{3x - 6} = 3^{15x - 30}$.
Putting it all together, the RHS becomes:
212z×224x×512x×315x−302^{12z} \times 2^{24x} \times 5^{12x} \times 3^{15x - 30}
Again, combining the exponents of the same base on the RHS:
For base 2: 12z+24x12z + 24x
For base 3: 15x−3015x - 30
For base 5: 12x12x
So, RHS simplifies to:
224x+12z×315x−30×512x2^{24x + 12z} \times 3^{15x - 30} \times 5^{12x}
Now, since the LHS and RHS must be equal, their exponents for each prime base must be equal. So, I can set up equations for each prime:
1
For base 2:
72x+24=24x+12z72x + 24 = 24x + 12z
2
For base 3:
12x=15x−3012x = 15x - 30
3
For base 5:
2y=12x2y = 12x
Let me solve these equations one by one.
Starting with base 3:
12x=15x−3012x = 15x - 30
Subtract 12x12x from both sides:
0=3x−300 = 3x - 30
Add 30 to both sides:
30=3x30 = 3x
Divide both sides by 3:
x=10x = 10
Okay, so x=10x = 10. That was straightforward.
Next, let's use this value of xx in the equation for base 5:
2y=12x2y = 12x
Substitute x=10x = 10:
2y=12×10=1202y = 12 \times 10 = 120
Divide both sides by 2:
y=60y = 60
Great, so y=60y = 60.
Now, moving on to the equation for base 2:
72x+24=24x+12z72x + 24 = 24x + 12z
Substitute x=10x = 10:
72×10+24=24×10+12z72 \times 10 + 24 = 24 \times 10 + 12z
Calculate each term:
720+24=240+12z720 + 24 = 240 + 12z
So,
744=240+12z744 = 240 + 12z
Subtract 240 from both sides:
744−240=12z744 - 240 = 12z
504=12z504 = 12z
Divide both sides by 12:
z=42z = 42
Alright, so z=42z = 42.
Now, we have x=10,y=60,andx = 10 , y = 60 , andz = 42$. Adding them together:
x+y+z=10+60+42=112x + y + z = 10 + 60 + 42 = 112
So, the sum is 112. That matches the given correct answer. I think I did everything correctly.
Expressed all terms as prime factors correctly.
Combined exponents on both sides accurately.
Solved each equation step by step without errors.
Substituted values correctly and performed arithmetic accurately.
Everything seems in order. I'm confident that the answer is indeed 112.
Final Answer The value of x+y+zx + y + z is \

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