Number of Trailing Zeros

How many trailing zeros are there in the number 3 4 × 4 5 × 5 6 3^4 \times 4^5 \times 5^6 ?


The answer is 6.

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9 solutions

Evan Huynh
Dec 21, 2015

In the above multiplication, we have 4 5 = 2 10 4^{5} = 2^{10} and 5 6 5^{6}

So there are 10 of TWO and 6 of FIVE.

We also know that 2 × 5 = 10 2 \times 5 = 10 is what account for a trailing zero. There are 6 of 2 × 5 2 \times 5 in the above multiplication. Hence, there would be 6 trailing zero.

Moderator note:

Simple standard approach accounting for the multiples of 2 and 5.

3^4 x 4^5 x 5^6 = (3x4x5)^4 x 4^1 x 5^2 = 60^4 x 100 = 6^4 x 10^4 x 10^2 Hence, there are 6 trailing zéros

Alexandre Jeannotte - 5 years, 5 months ago
Bloons Qoth
Jul 16, 2016

3 4 4 5 5 6 3 4 4 4 5 4 4 1 5 2 6 0 4 100 Therefore, there are 6 trailing zero’s 3^4*4^5*5^6 \\ 3^4*4^4*5^4*4^1*5^2 \\ 60^4*100 \\ \text{Therefore, there are 6 trailing zero's}

Xiaoying Qin
Dec 21, 2015

What is the title thing?

What do you call a mushroom that likes to go to parties? Fungi

Luis Ortiz - 5 years, 5 months ago

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Lol. Why is that the title though?

Xiaoying Qin - 5 years, 5 months ago

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Fungi = Funguy = 6 letters = 6 = Answer!

Harsh Shrivastava - 5 years, 5 months ago

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@Harsh Shrivastava True genius on this question

Oscar Shen - 5 years, 5 months ago
. .
Jul 24, 2020

3^4=81, 4^5=1024, 5^6=15625. 81 1024 15625=3^4 4^5 5^6. These are the same. 3^4 4^5 5^6=3^3 3, 4^5=4^4 4, 5^6=5^5 5 So 27 3 256 4 3125 5 This is 1.296e+9

Gia Hoàng Phạm
Oct 12, 2018

First 1 0 n = 2 n × 5 n 10^n=2^n \times 5^n so lets find them

We have find 4 5 4^5 which 4 = 2 2 4=2^2 and 5 6 5^6

Then we start:

4 5 × 5 6 = ( 2 2 ) 5 × 5 6 = 2 2 × 5 × 5 6 = 2 1 0 × 5 6 = 2 10 6 + 6 × 5 6 = 2 10 6 × 2 6 × 5 6 = 2 4 × ( 2 × 5 ) 6 = 2 4 × 1 0 6 4^5 \times 5^6=(2^2)^5 \times 5^6=2^{2 \times 5} \times 5^6=2^10 \times 5^6=2^{10-6+6} \times 5^6=2^{10-6} \times 2^6 \times 5^6=2^4 \times (2 \times 5)^6=2^4 \times 10^6

So the number of zero digits is 6 \boxed{\large{6}}

Zoe Codrington
Aug 27, 2018

2x5=10

Simple, but important.

You see, 5^6 is 6 fives, and 4^5 is 5 fours.

But one four is two twos.

So 4^5 is 10 twos.

That means there are 6 pairs of fives and twos multiplied together to be a ten

Ozge Cavas
Feb 18, 2018

3^4x4^5x5^6

=3^4x4^4x5^4x4x5^2

=60^4x10^2

=6^2x10^2x6^2x10^2x10^2

Which is 10^2x10^2x10^2 and that is 10^6 so it has 6 zeroes.

Thomas Sutcliffe
Nov 12, 2017

It so happens that all the above expressions are square numbers as well as higher powers. The square roots of each part of the above equation are 9, 32 and 125, so we are looking at (9 x 32 x 125) x (9 x 32 x 125) = (288 x 125) x (288 x 125) = 36,000 x 36,000. In that final equation we are multiplying a number with three trailing zeros by itself, so we will have six trailing zeros at the end of our final sum. For the record one last (straightforward) calculation gives us 1,296,000,000 as the actual answer.

Nikhil Raj
May 30, 2017

Relevant wiki: Trailing Number of Zeros

For trailing number of zeros, we need to find number of 10's we can get. For us, 3 4 3^{4} is useless as it will not help in finding 10. Here, highest power of 2 \rightarrow 2 10 \boxed{2^{10}} \\ . Also, highest power of 5 5 6 \rightarrow \boxed{5^{6}} \\ . So, we require to have highest number of 2 and 5. As a result we will take 2 6 × 5 6 = 1 0 6 \boxed{2^{6} \times 5^{6}} = \boxed{10^{6}} . So, total number of trailing zeros are 6 .

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