i need this answered it hurts my brain :C?

In a group of three numbers, the first number is twice the second number, and the third number is 15 less than the second number. If j is the third number and k is the sum of the first two numbers, which of the following equations represent the relationship between j and k ?

A 2j + 15 = k

B 2j + 30 = k

C 3j + 30 = k

D 3j + 45 = k

5 Answers

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  • 3 years ago
    Favorite Answer

    .

    let second number = x

    first number is twice second number: =========>first number = 2x

    third number is 15 less than the second number: =>third number = x - 15

    if

    (x - 15) = j

    x = j + 15

    ( 2x ) + ( x ) = k

    3x = k

    x = ⅓k

    Equate the two ‘x';

    j + 15 = ⅓k <===> 3j + 45 = k

    ANS: D

    ———

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    • King Leo
      Lv 7
      3 years agoReport

      It’s always better to have a better approach. If you could it would be nice to share approach.

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  • cidyah
    Lv 7
    3 years ago

    Let xyz be the number

    x = 2y

    j = y-15

    y=j+15

    k=x+y

    k= 2y+j+15

    k = 2(j+15)+j+15

    k = 2j+30+j+15

    k = 3j+45

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  • Philip
    Lv 6
    3 years ago

    Last sentence in question should end in "relationship between j and k?".

    The 3 numbers are p,q,j.

    p = 2q.

    j = q -15.

    k = p + q.

    p = 2q = 2(j + 15) = 2j + 30.

    q = j + 15.

    k = p + q = (2j + 30) + (j + 15) = 3j + 45 = 3(j + 15).

    Choice D pertains.

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  • ?
    Lv 7
    3 years ago

    Let's use h, i, j as the 3 numbers

    > k is the sum of the first two numbers

    TRANSLATION: k = h+i.......................[1]

    > the first number is twice the second number,

    TRANSLATION: h = 2i.........................[2]

    > the third number is 15 less than the second number.

    TRANSLATION: j = i-15.......................[3]

    So we have 3 equations to work with:

    k = h+i...............[1]

    h = 2i.................[2]

    j = i-15...............[3]

    Equation [3] can be rewritten solving for i:

    .....j = i-15...............[3]

    .....j+15 = i

    .....i = j+15..............[3a]

    The relationship between j and k is found as follows:

    Starting with [1], substitute for h from [2] into [1]

    .....k = h+i........[1]

    .....k = (2i)+i

    .....k = 3i..........[4]

    The relationship between k and j is found by

    substituting for i from [3a] into [4]

    .....k = 3(j+15)

    .....k = 3j + 45................ANS (Option D)

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  • 3 years ago

    Let j be the first number

    then the second number is j+15

    and the first number is 2j+30

    The sum of the first two numbers is 3j+45

    so k = 3j+45

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