It's a Digit World

Find the number of digits in:

( 2 2014 ) ( 5 2015 ) ( 1 0 2016 ) (2^{2014})(5^{2015})(10^{2016})

4032 4031 4030 4033

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3 solutions

2 2014 × 5 2015 × 1 0 2016 2^{2014} \times 5^{2015} \times 10^{2016}

= 2 2014 × 5 2014 × 5 × 1 0 2016 = 2^{2014} \times 5^{2014} \times 5 \times 10^{2016}

= 1 0 2014 × 5 × 1 0 2016 = 10^{2014} \times 5 \times 10^{2016}

= 5 × 1 0 4030 = 5 \times 10^{4030}

= 5 × 1 000...0000 4030 zeroes = 5 \times 1\underbrace{000...0000}_{\text{4030 zeroes}}

= 5 000...0000 4030 zeroes = 5\underbrace{000...0000}_{\text{4030 zeroes}}

So the total number of digits is the 4030 4030 zeroes plus the digit five in the front which gives us 4030 + 1 = 4031 4030 + 1 = \boxed{4031}

Ramiel To-ong
Feb 1, 2016

nice problem

Irtaza Sheikh
Apr 21, 2015

My solution is different and it is easy too..
Powers are in arthimetic progression then take any one or two examples to understand it.
2^3 ×5^4 ×10^5 = 5×10^8 =9
2^4 ×5^5 ×10^6 = 5×10^10 =11
By both examples we got it no.of digits are the addition of power of 5 and 10. Same we ll do in that case and get our answer.
2015+2016= 4031 Ans:



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