MK · 8 cards

Signed Numbers flashcards

8 cards with the formulas, rules and traps from this lesson. Answer in your head, then flip to check.

Rule · 1/8
Adding two signed numbers: what are the rules?
Same signs: add the absolute values and keep the common sign (−7 + (−5) = −12). Different signs: subtract the smaller absolute value from the larger and keep the sign of the larger (−12 + 5 = −7).
Rule · 2/8
How do you subtract a signed number?
Add its opposite: a − b = a + (−b). So 5 − (−8) = 5 + 8 = 13 and −4 − 7 = −4 + (−7) = −11. Subtracting a negative always makes the result larger.
Rule · 3/8
Sign rules for multiplying and dividing signed numbers?
Work with the absolute values, then attach the sign: like signs give a positive result, unlike signs a negative one. Examples: (−6)(−4) = 24 and −42 ÷ 7 = −6.
Strategy · 4/8
Product of many signed factors: how do you find the sign fast?
Count the negative factors first. An even count gives a positive product; an odd count gives a negative one. (−1)(−2)(−3)(5) has three negatives, so it equals −30.
Common trap · 5/8
Is $- 3^{2}$ the same as $(- 3)^{2}$ ?
No. In $- 3^{2}$ only 3 is squared and then negated, giving −9. In $(- 3)^{2}$ the base is −3, giving 9. An odd power of a negative base is negative: $(- 3)^{3} = - 27$ .
Common trap · 6/8
Which is greater, −12 or −3?
−3, because it lies to the right of −12 on the number line. Among negative numbers, the one with the larger absolute value is the smaller number.
Fact · 7/8
What happens with zero in signed operations?
Zero is neither positive nor negative. Any number times 0 is 0, and 0 divided by a nonzero number is 0, but division by 0 is undefined, so 7 ÷ 0 has no answer.
Formula · 8/8
How do you compute a change, such as a temperature change?
Change = final value − starting value. From −6°F to 11°F: 11 − (−6) = 17, a rise of 17°F. A negative result means the quantity decreased.

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