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Find the Number

Problem #99

Deadline to submit the solution: March 31st, 2003

A sum of  1/2, 1/3, and 1/7 of a number is 1 less than that number.

 

Q1: Find that number.

 
Solutions

 

Yvon Haessig from Canada
Grade: 6 Age: 12 School:
Solution:
Q1: 42

I made a table to find out that 1/2 = 3/6 and 1/3 = 2/6. Together that makes 5/6. Then i made a table to find out that 5/6 = 35/42 and 1/7 = 6/42. Together that makes 41/42. So the number 42 is the missing number.
About me: I am a home learner and I just learned all about this yesterday.
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Alex77 from Canada
Grade: 4 Age: 9 School:
Solution:
Q1: 42

x/2 + x/3 + x/7 = x - 1 42x/2 + 42x/3 + 42x/7 = 42x - 42 21x + 14x + 6x = 42x - 42 41x = 42x - 42 42x - 41x = 42 x = 42
Check: 42/2 + 42/3 + 42/7 = 42 - 1
21 + 14 + 6 = 41
41 = 41
About me: My number in hockey is 77.
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Kyle from USA
Grade: 6 Age: 11 School:
Solution:
Q1: 21
Q2: 14
Q3: 6

I changed the fractions to the least common denominator, added the numerators and subtracted 1 to get a solution the x = 40
About me: I like baseball football and tennis
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Britbux from USA
Grade: 5 Age: 11 School:
Solution:
Q1: 41/42

You need the same denominator. First, multiply 1/2 by 21 and you get 21/42. Next, you multiply 1/3 by 14 and you get 14/42. Then you multiply 1/7 by 6 and you get 6/42. Finally, add 21/42, 14/42 and 6/42 together to get a grand total of 41/42. (By the way is, yes, less than 1)
About me: I'm in advanced math.
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Arnold from Philippines
Grade: 5 Age: 11 School:
Solution:
Q1: 42

First, I tried to find a number that was divisible by 2, 3, and 7. The number was 42. One-half of 42 is 21, one-third of 42 is 14, and one-seventh of 42 is 6. Add up 21+14+6 and you get 41 - one less than 42.
About me: I represent my school in various national math contests. However the closest I've gotten to winning is third and that was in first grade.
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Allison from U.S.A
Grade: 5 Age: 11 School:
Solution:
Q1: 42

The lowest common denominator is 42. One half of 42 is 21, one third of 42 is 14, and one seventh of 42 is 6. When you add 21, 14, and 6 your sum is 41. This makes the mystery number 42. ( My mom helped me!)
About me: I am a Christian and love God alot. I also love my family. I am home schooled and love it. I have lots of great friends in Kentucky where I live. I LOVE to shop And I also LOVE school Really the reading Thanks for providing a great and fun website We like it alot
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yash S paranjape from INDIA
Grade: 9 Age: 14 School:
Solution:
Q1: X = 42

Let the number be x
x/2 + x/3 + x/7 = x-1
(21x+14x+6x)/42 = x-1
41x = 42x-42
41x - 42x = -42 -x=-42 x=42
Ans:.The required number is 42
About me: I am an INDIA .My name is yash paranjape from pune i like to watch tv and study i love mathematics
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Robin from Canada
Grade: 5 Age: 10 School:
Solution:
Q1: 42

First I found the LCD of 1/2, 1/3 and 1/7, which is 42. Next I found out what 1/2, 1/3 and 1/7 of 42, which is 1/2 x 42 = 21 1/3 x 42 = 14 1/7 x 42 = 6 21+14+6=41. Therefore 42 is the correct anwser
About me: I live in Richmond Hill Ontario Canada. I like to read and I am a rhythmic gymnast
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why from u.s.a
Grade: 7 Age: 19 School:
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baba from canada
Grade: 6 Age: 10 School:
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Cheryl from Bluegrove TX
Grade: Age: School:
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Nash112290 from United States
Grade: 6 Age: 12 School:
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Hayley from Connecticut
Grade: 7 Age: 12 School:
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