MaTh

Find the sum of all positive integers less than 1000 ending in 3 or 7.

  1. šŸ‘ 0
  2. šŸ‘Ž 0
  3. šŸ‘ 63
asked by Speedo
  1. First, you need to list all of the integers that match the condition. Do you know what these integers are?

    1. šŸ‘ 0
    2. šŸ‘Ž 0
    posted by Leo
  2. Positive integers less than 1000 consist of {1 ... 999}.

    This may also be written {001 ... 999}.

    So you need to count, {003, 007, 013, ... 987, 993, 997}.

    Which is the same result as counting {00, 01, ... 98, 99} twice over. (Once for ??3, once for ??7).

    Count the number of integers from 0 and 99 inclusive. Double that.

    1. šŸ‘ 0
    2. šŸ‘Ž 0
    posted by Graham
  3. I see it as
    (3 + 13 + 23 + + 993) + (7 + 17 + ... + 997)
    two arithmetic series,
    there are 100 terms in each series with a= 3 and d = 10 and a=7 and d=10
    using :
    sum= (n/2)(first + last)

    sum = (100/2)(3+993) + (100/2)(7+997)
    = 100,000

    1. šŸ‘ 0
    2. šŸ‘Ž 0
    posted by Reiny
  4. Thanks, guys!

    1. šŸ‘ 0
    2. šŸ‘Ž 0
    posted by Speedo

Respond to this Question

First Name

Your Response

Similar Questions

  1. MaTh

    Find the sum of all positive integers less than 1000 ending in 3 or 7.

    asked by mathemagiacian on August 31, 2013
  2. MaTh

    Find the sum of all positive integers less than 1000 ending in 3 or 7. What is the answer?

    asked by Speedo on September 2, 2013
  3. Maths

    The number 1000 can be written in several ways as a sum of one or more consecutive positive integers, for instance, 1000=1000 (one summand) or 1000=198+199+200+201+202 (five summands). Find the largest possible number of summands

    asked by HELP!! on May 8, 2013
  4. math

    Find the sum of the first one thousand positive integers. Explain how you arrived at your result. Now explain how to find the sum of the first n positive integers, where n is any positive integer, without adding a long list of

    asked by Anonymous on May 16, 2016
  5. Math

    Find the sum of all primes a

    asked by John on February 19, 2013
  6. math

    Find the sum of all integers m that are less than 1000 and equal to n!+1āˆ’āˆ’āˆ’āˆ’āˆ’āˆš for some positive integer n.

    asked by ayan on April 29, 2013
  7. ALGEBRA.

    The product of 2 positive integers is 1000. What is the smallest possible sum of these 2 integers?

    asked by HELP ME...uRGENT! on April 18, 2013
  8. math, algebra

    2a+2ab+2b I need a lot of help in this one. it says find two consecutive positive integers such that the sum of their square is 85. how would i do this one i have no clue i know what are positive integers.but i don't know how to

    asked by sana on January 26, 2007
  9. Math ( Number Theory )

    How many numbers from 1 to 1000 inclusive can be expressed as the sum of k >= 2 consecutive positive integers for some value of k ? Sorry to post question from Brilliant, I got 997 integers, but it's wrong. If you think you can

    asked by Lucy on April 9, 2013
  10. algebra!!!! please help me!!!!

    What is the sum of all positive integers Nā‰¤1000 such that N equals 13 times the digit sum of N?

    asked by fudgee on May 6, 2013

More Similar Questions