Question

A student is learning about positive and negative numbers with manipulatives. Each black cube represents + 1 , and each white cube represents − 1 . If there are currently 15 black cubes on the student's desk, how many white cubes must the student add to the desk for the combined value of the cubes to represent 0 ?

Answer 1

Answer:

15 white cubes

Step-by-step explanation:

Given

$White\ Cubes = -1$

$Black\ Cubes = +1$

$Number\ of\ Black\ Cubes = 15$

Required

Determine the number of white cubes needed to represent 0

To solve this question, we make use of the following equation.

$Black\ Cubes +White\ Cubes = 0$

If there are 15 black cubes, the the 15 black cubes is worth: +1 * 15

Substitute +1 * 15 for the Black Cubes

$+1 * 15 +White\ Cubes =0$

$+15 +White\ Cubes =0$

Collect Like Terms

$White\ Cubes = 0 - 15$

$White\ Cubes = - 15$

Recall that 1 white cube is worth -1

So, the number of white cubes is:

$Number = \frac{-15}{-1}$

$Number = 15$

Hence, the student needs 15 white cubes