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Evaluate absolute value as distance from zero

About 5 min

Questions stay in the language in which they were published.

These questions ask you to evaluate absolute values, compare them, find integers at a stated distance, or continue with an operation after the bars are resolved. The safest habit is to mark exactly what each pair of bars encloses.

Resolve the bars before the outside work

Read absolute value as distance from zero. The distance of -11 from zero is 11, the distance of 4 is 4, and the distance of zero is zero. A positive distance usually corresponds to two integers, one on each side of zero; for example, the integers at distance 5 are -5 and 5.

Expression shapeDecision method
One integer inside barsReturn its nonnegative distance from zero. The original side of zero no longer affects the result.
A calculation inside barsComplete the enclosed calculation first, then take the distance of that result; the absolute value of -6 plus 10, enclosed together, is 4.
A sign outside the barsEvaluate the bars first and then apply the outer sign; a minus outside the absolute value of -8 produces -8.
Further arithmetic outsideReplace each absolute value with its distance, then continue normally. The final result may be negative after subtraction or multiplication.

Separate bars matter. The absolute values of -4 and 10, taken separately and added, give 14, while the absolute value of their sum gives 6. Always follow the visible grouping instead of moving bars across a plus or minus sign.

Traps around the bars

Tempting routeHow to reject it
Carry a negative sign through the bars, or flip every positive valueThe bars report distance. They remove direction from a negative input and leave an already positive input unchanged.
Carry the order of negative values into their absolute valuesCompare the returned magnitudes instead. A negative farther from zero has the larger absolute value even though the original integer is smaller.
Cancel an outer minus with the minus insideThey act at different stages. The inner sign helps determine the distance; the outer sign acts on the finished distance.
Apply bars to just one term of an enclosed sumThe bars govern all the content between them. Finish that content as one calculation before measuring its distance.
Name only the positive integer at a positive distanceCheck both sides of zero. Two opposite integers share that same distance.
Stretch the bars over a later multiplicationBars affect only what they visibly enclose. Resolve them, then use the ordinary sign rule for the remaining product.

Try it

Question 25

Enter the value of |-9|.

Question 32

Work out |-4| + |6| and then |-4 + 6|. Which pair of values is correct, in that order?

  1. 10 and 2
  2. 2 and 10
  3. 10 and 10
  4. 2 and 2
Question 35

Enter the value of |-7| - |-10|.

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Evaluate absolute value as distance from zero · Questena