Results 1 to 3 of 3

Math Help - easy Digits problem and Semicircle.. - fastest way to solve it? Otherwise easy

  1. #1
    Newbie
    Joined
    Sep 2011
    Posts
    6

    easy Digits problem and Semicircle.. - fastest way to solve it? Otherwise easy

    Hello

    im not sure what the fastest way to solve this is..
    please let me know.. thanks!



    22. A and B are letters representing different digits from 1 to 9.
    Given:

    AB
    X 7
    -----
    4BB


    A-B=?


    (I) 1
    (2) 2
    (3) 3
    (4) -1

    answer: 1
    need 5 bc 7*5= 35.. b needs to be 5.
    ..
    defiitely 5.
    definitely need a 6 because 60 * 7 is 420 ish..
    7 is too high
    ..
    so 6-5 =1


    not sure if this is the fastest way! thanks!


    21.
    A certain 2 digit number is known to be 3 times as great as the sum of its digits. What is the product of its digits?

    1. 12
    2. 14
    3. 16.
    4. 18

    answer: 2

    27 is 3x greater than 2+7 = 9.
    2*7 is 14.

    not sure how to do this FAST without going backwards?




    -------------------

    Semicircle.. shaded region

    q21

    the legs of a triangle ABC are 2 and 4. it is in a semicircle. and is painted white. the rest of the semicircle is black. what is the area of the black?

    i know that answer must have -4 because 1/2 * 2 * 4 = 4.


    the area..
    2^2 + 4^2 = hyp^2
    4 + 16 = 20, hyp is root 20
    pi* (1/2 root 20 )^2 = total area.
    20/4 = 5
    so 5pi - 4??
    huh
    ---
    PS is there a way to post pictures up here? other people did it and i'd like to know how!
    Attached Thumbnails Attached Thumbnails easy Digits problem and Semicircle.. - fastest way to solve it? Otherwise easy-halfcircle.jpg  
    Last edited by jsvlad; September 14th 2011 at 05:08 AM. Reason: attractive
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Member
    Joined
    Oct 2010
    From
    Mumbai, India
    Posts
    203

    Re: easy Digits problem and Semicircle.. - fastest way to solve it? Otherwise easy

    I thinks its probably fastest the way you have done
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Junior Member
    Joined
    Jan 2013
    From
    India
    Posts
    30
    Thanks
    4

    Re: easy Digits problem and Semicircle.. - fastest way to solve it? Otherwise easy

    22. A and B are letters representing different digits from 1 to 9.
    Given:
    AB
    X 7
    -----
    4BB
    B 7 = B
    B = 0 or 5
    if B = 0 then A 7 = 40
    none of value of integer value satisfy the condition
    so B = 5
    A 5
    7
    ---------
    455
    calculate directly 455/7 = 65
    A = 6
    or A 7 + 3 (c/f) = 45
    or A 7 = 42
    A = 6
    A - B = 6 7 = 1

    (4) -1

    A certain 2 digit number is known to be 3 times as great as the sum of its digits. What is the product of its digits?
    Let the digits in the number be ab
    then number is 10a + b
    10a + b = 3(a + b)
    10a + b = 3a + 3b
    7a = 2b
    a = 2, b = 7
    a b = 14

    2. 14
    ----
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. [SOLVED] 2 easy questions: Probability/Percentages and Digits
    Posted in the Algebra Forum
    Replies: 3
    Last Post: September 13th 2011, 10:34 PM
  2. Easy-to-solve doubt! Please help me!
    Posted in the Statistics Forum
    Replies: 1
    Last Post: September 7th 2010, 11:12 AM
  3. Solve for x (easy)!
    Posted in the Algebra Forum
    Replies: 2
    Last Post: March 31st 2010, 12:19 AM
  4. I can't solve this easy question ?
    Posted in the Pre-Calculus Forum
    Replies: 3
    Last Post: December 8th 2009, 01:57 AM
  5. Seemingly easy question... too easy.
    Posted in the Pre-Calculus Forum
    Replies: 3
    Last Post: August 23rd 2009, 09:36 PM

Search Tags


/mathhelpforum @mathhelpforum