12 multiple-choice questions, progressively harder.
Evaluate (−2)4(-2)^4(−2)4.
Solution
Correct answer: A
The parentheses make −2-2−2 the base, and four negative factors multiply to a positive.
(−2)4=(−2)(−2)(−2)(−2)=16(-2)^4 = (-2)(-2)(-2)(-2) = 16(−2)4=(−2)(−2)(−2)(−2)=16
An even number of negative factors gives a positive result.
Evaluate −24-2^4−24.
Correct answer: B
Without parentheses the exponent applies only to the 222, and the minus sign comes after.
−24=−(24)=−16-2^4 = -(2^4) = -16−24=−(24)=−16
Compare with (−2)4=16(-2)^4 = 16(−2)4=16, where the parentheses make −2-2−2 the base.
Which of these is the largest?
Compute each value, then compare.
210=1024,102=100,35=243,53=1252^{10} = 1024, \quad 10^2 = 100, \quad 3^5 = 243, \quad 5^3 = 125210=1024,102=100,35=243,53=125
The largest is 210=10242^{10} = 1024210=1024.
A colony of bacteria doubles every hour. Starting from 111 bacterium, how many are there after 666 hours?
Correct answer: D
Doubling 666 times multiplies by 222 six times.
26=642^6 = 6426=64
It is not 6×2=126 \times 2 = 126×2=12; the count of doublings is the exponent.
Evaluate 23×522^3 \times 5^223×52.
Evaluate each power separately, then multiply the results.
23=8,52=25,8×25=2002^3 = 8, \quad 5^2 = 25, \quad 8 \times 25 = 20023=8,52=25,8×25=200
Which is greater, 2162^{16}216 or 16216^2162?
Correct answer: C
Compute each value.
162=256,216=65,53616^2 = 256, \qquad 2^{16} = 65{,}536162=256,216=65,536
So 2162^{16}216 is far greater. Here the exponent matters much more than the base.
Evaluate 100−62×2100 - 6^2 \times 2100−62×2.
Power first, then multiplication, then subtraction.
62=36,36×2=72,100−72=286^2 = 36, \quad 36 \times 2 = 72, \quad 100 - 72 = 2862=36,36×2=72,100−72=28
If 3x=813^x = 813x=81, what is xxx?
Multiply 333's until you reach 818181.
3×3×3×3=813 \times 3 \times 3 \times 3 = 813×3×3×3=81
That is four factors, so x=4x = 4x=4.
Evaluate 22×232^2 \times 2^322×23 (work out each power, then multiply).
Evaluate each power, then multiply the results.
22=4,23=8,4×8=322^2 = 4, \quad 2^3 = 8, \quad 4 \times 8 = 3222=4,23=8,4×8=32
Which expression has the largest value?
33=27,25=32,62=36,42=163^3 = 27, \quad 2^5 = 32, \quad 6^2 = 36, \quad 4^2 = 1633=27,25=32,62=36,42=16
The largest is 62=366^2 = 3662=36.
Evaluate 5+2×425 + 2 \times 4^25+2×42.
Power first, then multiplication, then addition.
42=16,2×16=32,5+32=374^2 = 16, \quad 2 \times 16 = 32, \quad 5 + 32 = 3742=16,2×16=32,5+32=37
Evaluate 103−10210^3 - 10^2103−102.
Evaluate each power, then subtract.
103=1000,102=100,1000−100=90010^3 = 1000, \quad 10^2 = 100, \quad 1000 - 100 = 900103=1000,102=100,1000−100=900
It is not 103−2=1010^{3-2} = 10103−2=10; subtract the values, not the exponents.
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