12 multiple-choice questions, progressively harder.
Evaluate ∣(−3)+(−9)∣\lvert (-3) + (-9) \rvert∣(−3)+(−9)∣.
Solution
Correct answer: A
Add inside the bars first. Two negatives combine further left: −3-3−3 and −9-9−9 give −12-12−12.
∣(−3)+(−9)∣=∣−12∣=12\lvert (-3) + (-9) \rvert = \lvert -12 \rvert = 12∣(−3)+(−9)∣=∣−12∣=12
How many integers sit exactly 666 units from zero? (In symbols: how many integers nnn have ∣n∣=6\lvert n \rvert = 6∣n∣=6?)
Correct answer: B
An integer six units from zero can sit on either side of zero.
∣6∣=6and∣−6∣=6\lvert 6 \rvert = 6 \quad\text{and}\quad \lvert -6 \rvert = 6∣6∣=6and∣−6∣=6
Those are the two integers, 666 and −6-6−6.
Evaluate ∣4×(−3)∣\lvert 4 \times (-3) \rvert∣4×(−3)∣.
Correct answer: C
The bars group the product, so multiply inside first. A positive times a negative is negative, giving −12-12−12, and then the bars measure its distance from zero.
∣4×(−3)∣=∣−12∣=12\lvert 4 \times (-3) \rvert = \lvert -12 \rvert = 12∣4×(−3)∣=∣−12∣=12
Evaluate ∣−2∣+∣−3∣+∣−4∣\lvert -2 \rvert + \lvert -3 \rvert + \lvert -4 \rvert∣−2∣+∣−3∣+∣−4∣.
Correct answer: D
Each pair of bars is its own group, so take each absolute value, then add.
∣−2∣+∣−3∣+∣−4∣=2+3+4=9\lvert -2 \rvert + \lvert -3 \rvert + \lvert -4 \rvert = 2 + 3 + 4 = 9∣−2∣+∣−3∣+∣−4∣=2+3+4=9
Which number has the greatest absolute value: −14-14−14, 111111, −9-9−9, or 131313?
Take the absolute value of each, since the question asks about distance from zero.
∣−14∣=14,∣11∣=11,∣−9∣=9,∣13∣=13\lvert -14 \rvert = 14, \quad \lvert 11 \rvert = 11, \quad \lvert -9 \rvert = 9, \quad \lvert 13 \rvert = 13∣−14∣=14,∣11∣=11,∣−9∣=9,∣13∣=13
The greatest distance is 141414, from −14-14−14.
How many integers sit 222 units or less from zero?
Start at zero and go no further than two units in either direction. List what you land on: −2,−1,0,1,2-2, -1, 0, 1, 2−2,−1,0,1,2.
∣−2∣=2, ∣−1∣=1, ∣0∣=0, ∣1∣=1, ∣2∣=2\lvert -2 \rvert = 2, \; \lvert -1 \rvert = 1, \; \lvert 0 \rvert = 0, \; \lvert 1 \rvert = 1, \; \lvert 2 \rvert = 2∣−2∣=2,∣−1∣=1,∣0∣=0,∣1∣=1,∣2∣=2
That is five integers.
Evaluate ∣−20÷5∣\lvert -20 \div 5 \rvert∣−20÷5∣.
The bars group the quotient, so divide inside first. A negative divided by a positive is negative, giving −4-4−4, and then the bars measure its distance from zero.
∣−20÷5∣=∣−4∣=4\lvert -20 \div 5 \rvert = \lvert -4 \rvert = 4∣−20÷5∣=∣−4∣=4
Which statement is true?
A number and its opposite share one absolute value, because both are the same distance from zero.
∣−8∣=8=∣8∣\lvert -8 \rvert = 8 = \lvert 8 \rvert∣−8∣=8=∣8∣
So the third statement is true. The first gives 161616, the second a negative, and the fourth a false inequality.
Evaluate ∣−5∣−∣2−9∣\lvert -5 \rvert - \lvert 2 - 9 \rvert∣−5∣−∣2−9∣.
Evaluate each group. The first is ∣−5∣=5\lvert -5 \rvert = 5∣−5∣=5, and the second is ∣2−9∣=∣−7∣=7\lvert 2 - 9 \rvert = \lvert -7 \rvert = 7∣2−9∣=∣−7∣=7.
5−7=−25 - 7 = -25−7=−2
The minus between the two groups keeps its meaning, so the result can be negative.
Evaluate ∣(−4)+4∣+∣−6−2∣\lvert (-4) + 4 \rvert + \lvert -6 - 2 \rvert∣(−4)+4∣+∣−6−2∣.
Evaluate inside each pair of bars first. The first is ∣(−4)+4∣=∣0∣=0\lvert (-4) + 4 \rvert = \lvert 0 \rvert = 0∣(−4)+4∣=∣0∣=0, and the second is ∣−6−2∣=∣−8∣=8\lvert -6 - 2 \rvert = \lvert -8 \rvert = 8∣−6−2∣=∣−8∣=8.
0+8=80 + 8 = 80+8=8
Which list is ordered from greatest to least by absolute value: −9-9−9, 333, −5-5−5, 888?
Take the absolute value of each: ∣−9∣=9\lvert -9 \rvert = 9∣−9∣=9, ∣3∣=3\lvert 3 \rvert = 3∣3∣=3, ∣−5∣=5\lvert -5 \rvert = 5∣−5∣=5, ∣8∣=8\lvert 8 \rvert = 8∣8∣=8.
9>8>5>39 > 8 > 5 > 39>8>5>3
Ordering the original numbers by those distances, greatest first, gives −9, 8, −5, 3-9,\; 8,\; -5,\; 3−9,8,−5,3.
If ∣x∣=10\lvert x \rvert = 10∣x∣=10 and xxx is positive, what is xxx?
Two integers are ten units from zero: 101010 and −10-10−10. The condition that xxx is positive selects one.
∣10∣=10 and 10>0\lvert 10 \rvert = 10 \text{ and } 10 > 0∣10∣=10 and 10>0
So x=10x = 10x=10. The sign condition removes the ambiguity that ∣x∣=10\lvert x \rvert = 10∣x∣=10 alone would leave.
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