37 and 0s

We divide the number below by 37.

3 0000 0000 Number of 0 = 99 7 3\underbrace{0000\dots 0000}_{\text{Number of} \ 0=99}7

If the remainder is R R , and the quotient's first 9 digits are a b c d e f g h i \overline{abcdefghi} , then find the value of

1 + R + a b c d e f g h i 1+R+\overline{abcdefghi}


The answer is 810810811.

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1 solution

Marco Brezzi
Aug 16, 2017

Let

n = 3 00 0 99 7 n=3\underbrace{00\ldots 0}_{99} 7

To prove that n n is divisible by 37 37 I'll use two numbers that are clearly divisible by 37 37 .

Let's consider

a = 37 + 370 + 3700 + + 37 00 0 99 = 4 11 1 98 07 = 37 11 1 100 \begin{aligned} a=37+370+3700+\ldots +37\underbrace{00\ldots 0}_{99}&=4\underbrace{11\ldots 1}_{98} 07\\ &=37\cdot \underbrace{11\ldots 1}_{100} \end{aligned}

and

b = 11 1 99 00 = 111 100100 100 33 times the string 100 = 37 300300 300 33 times the string 300 \begin{aligned} b=\underbrace{11\ldots 1}_{99}00 &=111\cdot\underbrace{100100\ldots 100}_{33 \text{ times the string } 100}\\ &=37\cdot\underbrace{300300\ldots 300}_{33 \text{ times the string } 300} \end{aligned}

We can see that n = a b n=a-b so n n is divisible by 37 37 so the remainder is R = 0 R=0

The quotient is

11 1 100 300300 300 33 times the string 300 = 810810 810810 32 times the string 810 811 \underbrace{11\ldots 1}_{100}-\underbrace{300300\ldots 300}_{33 \text{ times the string } 300}=\underbrace{810810\ldots 810810}_{32 \text{ times the string } 810}811

Thus the answer is

a b c d e f g h i + R + 1 = 810810810 + 0 + 1 = 810810811 \overline{abcdefghi}+R+1=810810810+0+1=\boxed{810810811}

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