Question

Divya spends all of her free time playing with her building blocks. She owns building block sets with 333 pieces, 555 pieces, and 101010 pieces. Divya knows she owns 555 sets with 555 pieces and 222 sets with 101010 pieces. She also knows that she averages 555 pieces per set. This information is summarized in the table below

Answer 1

Answer:

  5 sets

Step-by-step explanation:

The average number of pieces per set is the ratio of the total number of pieces to the total number of sets.

Let x represent the number of 3-piece sets. Then the total number of pieces is ...

  3x +5(5) +10(2) = 3x +45

The total number of sets is ...

  x +5 +2 = x +7

We want the ratio of these numbers to be 5 pieces per set:

  (3x +45)/(x +7) = 5

  3x +45 = 5x +35 . . . . . multiply by (x+7)

  10 = 2x . . . . . . . . . . subtract (3x+35)

  5 = x . . . . . . . . . divide by 2

Divya owns 5 sets with 3 pieces.

_____

Alternate solution

Each 10-piece set has 5 more pieces than average, so the two of them total 10 more pieces than average.

Each 3-piece set has 2 fewer pieces than average. The total number of 3-piece sets must have a total of 10 fewer pieces than average in order to balance the excess of the 10-piece sets. That is, there must be 10/2 = 5 of the 3-piece sets to have a total lof 10 fewer pieces than average.

Altogether, the differences from average must total zero.