Find zeros

Algebra Level 2

2 5 5 × 15 0 4 × 200 8 3 25^5\times 150^4 \times 2008^3

Find the number of trailing zeros of the expression above.


The answer is 13.

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2 solutions

Mahdi Raza
May 7, 2020

= 2 13 × 3 4 × 5 18 × 25 1 3 = 3 4 × 5 5 × 25 1 3 × ( 1 0 13 ) 13 \begin{aligned} &= 2^{13} \times 3^4 \times 5^{18} \times 251^3 \\ &= 3^{4} \times 5^{5} \times 251^{3} \times (10^{13}) \implies \boxed{13} \end{aligned}

Tom Engelsman
May 6, 2020

Taking 200 8 3 = 2 9 25 1 3 2008^3 = 2^{9}251^{3} and 2 5 5 = 5 10 25^5 = 5^{10} we obtain 200 8 3 2 5 5 = ( 2 5 ) 9 5 1 25 1 3 = ( 5 1 25 1 3 ) 1 0 9 2008^3 \cdot 25^5 = (2 \cdot 5)^{9} 5^1 251^3 = (5^1 251^3) \cdot 10^9 . Now the final product can compute to:

( 5 1 25 1 3 ) 1 0 9 × ( 1 5 4 ) 1 0 4 = ( 3 4 5 5 25 1 3 ) 1 0 13 13 (5^1 251^3) \cdot 10^9 \times (15^4) \cdot 10^4 = (3^4 5^5 251^3) \cdot 10^{13} \Rightarrow \boxed{13} trailing zeros.

My explanation is also pretty much the same! Great!

Mahdi Raza - 1 year, 1 month ago

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