12 multiple-choice questions, progressively harder.
Evaluate 2×[ 3+2×(4−1) ]2 \times [\,3 + 2 \times (4 - 1)\,]2×[3+2×(4−1)].
Solution
Correct answer: A
Work from the innermost group outward, applying the tiers inside each group.
2×[ 3+2×(4−1) ]=2×[ 3+2×3 ]2 \times [\,3 + 2 \times (4 - 1)\,] = 2 \times [\,3 + 2 \times 3\,]2×[3+2×(4−1)]=2×[3+2×3]
Inside the bracket, multiply before adding.
2×[ 3+6 ]=2×9=182 \times [\,3 + 6\,] = 2 \times 9 = 182×[3+6]=2×9=18
Where must parentheses go to make 2+3×4=202 + 3 \times 4 = 202+3×4=20 true?
Correct answer: C
Group the addition so it happens before the multiplication.
(2+3)×4=5×4=20(2 + 3) \times 4 = 5 \times 4 = 20(2+3)×4=5×4=20
Without parentheses the value is 141414, and 2+(3×4)2 + (3 \times 4)2+(3×4) is also 141414.
A student evaluated 20÷4×520 \div 4 \times 520÷4×5 as 111. What is the correct value?
Division and multiplication share one tier, so work left to right.
20÷4×5=5×5=2520 \div 4 \times 5 = 5 \times 5 = 2520÷4×5=5×5=25
The student did 4×5=204 \times 5 = 204×5=20 first, then 20÷20=120 \div 20 = 120÷20=1, treating multiplication as if it always came before division.
Evaluate 48÷(2×4)+148 \div (2 \times 4) + 148÷(2×4)+1.
Settle the group, then divide, then add.
48÷(2×4)+1=48÷8+148 \div (2 \times 4) + 1 = 48 \div 8 + 148÷(2×4)+1=48÷8+1
Divide, then add.
48÷8+1=6+1=748 \div 8 + 1 = 6 + 1 = 748÷8+1=6+1=7
Evaluate 3+2×[ 10−(22+3) ]3 + 2 \times [\,10 - (2^2 + 3)\,]3+2×[10−(22+3)].
Work from the innermost group outward; the exponent goes before the addition inside it.
3+2×[ 10−(22+3) ]=3+2×[ 10−7 ]3 + 2 \times [\,10 - (2^2 + 3)\,] = 3 + 2 \times [\,10 - 7\,]3+2×[10−(22+3)]=3+2×[10−7]
Finish the bracket, then multiply, then add.
3+2×3=3+6=93 + 2 \times 3 = 3 + 6 = 93+2×3=3+6=9
Where must parentheses go to make 12−6÷3=212 - 6 \div 3 = 212−6÷3=2 true?
Correct answer: B
Group the subtraction so it happens before the division.
(12−6)÷3=6÷3=2(12 - 6) \div 3 = 6 \div 3 = 2(12−6)÷3=6÷3=2
Without parentheses the value is 101010, and 12−(6÷3)12 - (6 \div 3)12−(6÷3) is also 101010.
Evaluate 42+83×2\dfrac{4^2 + 8}{3} \times 2342+8×2.
The bar groups the whole numerator, so settle it first; the exponent goes before the addition.
42+83×2=16+83×2=243×2\frac{4^2 + 8}{3} \times 2 = \frac{16 + 8}{3} \times 2 = \frac{24}{3} \times 2342+8×2=316+8×2=324×2
The line is now 24÷3×224 \div 3 \times 224÷3×2. Division and multiplication share one tier, so work left to right: divide, then multiply.
8×2=168 \times 2 = 168×2=16
Evaluate 100−2×(3+2)2100 - 2 \times (3 + 2)^2100−2×(3+2)2.
Settle the group, then square, then multiply, then subtract.
100−2×(3+2)2=100−2×52=100−2×25100 - 2 \times (3 + 2)^2 = 100 - 2 \times 5^2 = 100 - 2 \times 25100−2×(3+2)2=100−2×52=100−2×25
Multiply, then subtract.
100−50=50100 - 50 = 50100−50=50
Evaluate 302+3+2×32\dfrac{30}{2 + 3} + 2 \times 3^22+330+2×32.
Correct answer: D
The bar groups the denominator, so settle the fraction; handle the exponent and multiplication separately.
302+3+2×32=305+2×9=6+18\frac{30}{2 + 3} + 2 \times 3^2 = \frac{30}{5} + 2 \times 9 = 6 + 182+330+2×32=530+2×9=6+18
Then add.
6+18=246 + 18 = 246+18=24
A student flattened 8+42+2\dfrac{8 + 4}{2 + 2}2+28+4 to 8+4÷2+28 + 4 \div 2 + 28+4÷2+2 and got 121212. What is the correct value?
The fraction bar groups the whole numerator and the whole denominator, so it must be written (8+4)÷(2+2)(8 + 4) \div (2 + 2)(8+4)÷(2+2).
8+42+2=124=3\frac{8 + 4}{2 + 2} = \frac{12}{4} = 32+28+4=412=3
Dropping the grouping turned the line into 8+4÷2+28 + 4 \div 2 + 28+4÷2+2, where the division acts on only the 444. That gives 4÷2=24 \div 2 = 24÷2=2, then 8+2+2=128 + 2 + 2 = 128+2+2=12, dividing one term instead of the whole top by the whole bottom.
Evaluate 23÷4+3×(5−2)22^3 \div 4 + 3 \times (5 - 2)^223÷4+3×(5−2)2.
Settle the group, then the exponents, then the multiplication and division, then add.
23÷4+3×(5−2)2=8÷4+3×32=2+3×9=2+272^3 \div 4 + 3 \times (5 - 2)^2 = 8 \div 4 + 3 \times 3^2 = 2 + 3 \times 9 = 2 + 2723÷4+3×(5−2)2=8÷4+3×32=2+3×9=2+27
2+27=292 + 27 = 292+27=29
Evaluate (8−3)2−14+22\dfrac{(8 - 3)^2 - 1}{4} + 2^24(8−3)2−1+22.
Settle the fraction, whose bar groups its numerator, then add the squared term.
(8−3)2−14+22=52−14+4=244+4=6+4\frac{(8 - 3)^2 - 1}{4} + 2^2 = \frac{5^2 - 1}{4} + 4 = \frac{24}{4} + 4 = 6 + 44(8−3)2−1+22=452−1+4=424+4=6+4
6+4=106 + 4 = 106+4=10
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