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When the celebrated German mathematician Karl Friedrich Gauss (1777-1855) was nine he was asked to add all the integers from 1 through 100. He quickly added 1 to 100, 2 to 99, and so on for 50 pairs of numbers each adding to 101. Answer: 50 X 101=5,050. What is the sum of all the digits in integers from 1 through 1,000,000,000? (That’s all the digits in all the numbers, not all the numbers themselves.)
Answer: The numbers can be grouped by pairs: 999,999,999 and 0; 999,999,998 and 1' 999,999,997 and 2; and so on.... There are half a billion pairs, and the sum of the digits in each pair is 81. The digits in the unpaired number, 1,000,000,000, add to 1. Then: (500,000,000 X 81) + 1= 40,500,000,001.
Solution:
Show Answer
The numbers can be grouped by pairs:
999,999,999 and 0;
999,999,998 and 1′
999,999,997 and 2;
and so on….
There are half a billion pairs, and the sum of the digits in each pair is 81. The digits in the unpaired number, 1,000,000,000, add to 1. Then:
(500,000,000 X 81) + 1= 40,500,000,001.
Show Answer
999,999,999 and 0;
999,999,998 and 1′
999,999,997 and 2;
and so on….
There are half a billion pairs, and the sum of the digits in each pair is 81. The digits in the unpaired number, 1,000,000,000, add to 1. Then:
(500,000,000 X 81) + 1= 40,500,000,001.
At the bottom of the ocean there is a treasure chest. It has everything except for one thing. What is it? answer
Answer: Air or Key
Solution:
Puzzle answer: At the bottom of the sea there’s a treasure chest. It has everything except for one thing. What is it?
Click below to see brain teaser riddle questions with answers and Share your answers and thoughts in the comments box below
Show answer
Answer: Air or Key
Knowledge increases by sharing 🙂
Puzzle answer: At the bottom of the sea there’s a treasure chest. It has everything except for one thing. What is it?
Click below to see brain teaser riddle questions with answers and Share your answers and thoughts in the comments box below
Show answer
Answer: Air or Key
Knowledge increases by sharing 🙂



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