ACT Form B05 Math Answer Explanation



2018 December(B05) Math Question 1

Graphing Properties

- Interpret Graphs or Figures


Choice G

$$t=10 \Rightarrow 180(t-2)=180(10-2)=180\times8=1440$$


Choice D

$$(-8,-3)\Rightarrow (-8+8,-3+3)=(0,0)$$


Choice C

$$\frac{1}{3}\pi r^{2}h,\ r=3,\ h=6$$ $$\Rightarrow \frac{1}{3}\pi\times3^{2}\times6=18\pi$$


Choice G

$$(x^{4})^{6}=x^{4\times6}=x^{24}$$


2018 December(B05) Math Question 7

Word Problems

- 1 Variable Equations


Choice C

$$$12\times40+$12\times1\frac{1}{2}\times5$$ $$=$480+$90$$ $$=$570$$


2018 December(B05) Math Question 8

Matrices

- Addition & Subtraction


Choice F

$$=\begin{bmatrix}5+(-6) & 7+3 \\(-4)+6 & 4+8 \end{bmatrix}$$ $$=\begin{bmatrix}-1 & 10 \\2 & 12 \end{bmatrix}$$


2018 December(B05) Math Question 9

Probability

- Combinations


Choice E

$$6\times4\times6=144$$


2018 December(B05) Math Question 10

Conics

- Parabola


Choice G

b05

$$(a,0)=(-1+2,0)=(1,0)$$ $$\Rightarrow a=1$$


Choice B

b05

$$3\times8\times7\times1\times2=336$$


2018 December(B05) Math Question 12

Equation of a Line

- Equations that Describe a Line


Choice J

$$\frac{y_{2}-y_{1}}{x_{2}-x_{1}}=\frac{4-3}{2-(-7)}=\frac{1}{9}$$


Choice A

$$60\times\frac{1}{2}=30$$ $$60\times\frac{1}{4}=15$$ $$60\times\frac{1}{6}=10$$ $$60-30-15-10=5$$


2018 December(B05) Math Question 14

Inequalities

- Inequality Expressions


Choice J

$$6x-2\leq11.2$$ $$\Rightarrow 6x\leq13.2$$ $$\Rightarrow x\leq2.2$$

2 is the greatest solution.


2018 December(B05) Math Question 15

Word Problems

- Fixed Cost + Variable Cost


Choice D

$$17.5+0.7x\leq50$$ $$\Rightarrow 0.7x\leq 32.5$$ $$\Rightarrow x\leq46.42...$$ $$Ans:\ x=46$$


Choice K

$$2:9=8:x$$ $$\Rightarrow x=\frac{8}{2}\times9=36$$


2018 December(B05) Math Question 17

Statistics

- Mean, Median


Choice C

$$Total=30\times5=150$$ $$150-50=100$$ $$100\div4=25$$


2018 December(B05) Math Question 18

Angles

- Parallel Lines


Choice K

b05

$$\because\overline{BE}\equiv\overline{BF}$$ $$\therefore ABE=\angle CBF=32°$$ $$\because\overline{AC}\parallel\overline{DF}$$ $$\therefore\angle ABE=\angle BEF=32°$$ $$\angle BED=180°-32°=148°$$


Choice C

$$x=-1, y=2, $$ $$x^{3}-2x^{2}y-4xy^{2}+8$$ $$=(-1)^{3}-2(-1)^{2}\times2-4(-1)\times2^{2}+8$$ $$=-1-2\times2+4\times4+8$$ $$=-1-4+16+8$$ $$=19$$


Choice H

$$A: 10\times5+12\times10+5\times6=200$$ $$B: 10\times5.5+12\times9.5+5\times5.75$$ $$=55+114+28.75$$ $$=197.75$$ $$200-197.75=2.25$$


2018 December(B05) Math Question 21

Equation of a Line

- Equations that Describe a Line


Choice E

b05

$$Slope\ l=1$$ $$\Rightarrow Slope\ p=1\times\frac{1}{2}=\frac{1}{2}$$ …


2018 December(B05) Math Question 22

Trigonometry

- Pythagorean Theorem & sin cos tan


Choice H

b05

$$\sin\theta=\frac{a}{\sqrt{a^{2}+b^{2}}}$$


Choice E

b05

$$50\times50=2500$$ $$10\times x=2500$$ $$\Rightarrow x=250$$


2018 December(B05) Math Question 24

Algebraic & Function Expressions

- Nested Functions


Choice J

$$(fg)(x)=(5x^{2}-6x+1)(x^{2}-2)$$ $$=(5x^{2}-6x+1)(x^{2})-(5x^{2}-6x+1)2$$ $$=(5x^{4}-6x^{3}+x^{2})-10x^{2}+12x-2$$ $$=5x^{4}-6x^{3}-9x^{2}+12x-2$$


2018 December(B05) Math Question 25

Probability

- One Event


Choice B

$$Total\ marbles:\ 12+14+8=34$$ $$p(red)=\frac{12+x}{34+x}=\frac{3}{5}$$ $$5(12+x)=3(34+x)$$ …


Choice H

b05

$$Megan:\frac{120}{40}=3$$ $$Louisa:\frac{120}{70}=1\frac{5}{7}\approx1.71$$


Choice E

$$\require{cancel} $$ $$3x-(x+6)+8=2x+14$$ $$\Rightarrow3x-x-6+8=2x+14$$ $$\Rightarrow\cancel{2x}+2=\cancel{2x}+14$$ …


2018 December(B05) Math Question 28

Statistics

- Mean, Median, Mode Combinations


Choice F

$$Mean:(\frac{1+2+3+4+5+6+7}{2})\div7$$ $$=\frac{[(1+7)7]\div2}{2}\div7$$ $$=\frac{56\div2}{2}\div7$$ $$=\frac{28}{2}\div7$$ $$=14\div7$$ …


2018 December(B05) Math Question 29

Number Types & Properties

- Complex Number


Choice C

$$(-2i+5)(2i+5)=(-2i)2i+(-2i)5+5(2i)+5(5)$$ $$=-4i^{2}-10i+10i+25=25-4i^{2}$$ $$Since\ i^{2}=-1,$$ $$\Rightarrow …


Choice H

$$3.8\times10^{5}+6.4\times10^{4}$$ $$=3.8\times10^{1}\times10^{4}+6.4\times10^{4}$$ $$=38\times10^{4}+6.4\times10^{4}$$ $$=(38+6.4)\times10^{4}$$ $$=44.4\times10^{4}$$ …


Choice B

b05


Choice F

b05

$$350\ miles\ of\ highway\ driving.$$ …


Choice B

$$$2400\div$4/gallon=600$$ $$600\times25=15000$$


Choice H

$$2400\times5=12000$$ $$12000+3500=15500$$ $$15500\div5=3100$$


2018 December(B05) Math Question 35

Word Problems

- Distance, Speed, Time


Choice C

$$240\ miles=240\times5280\ feet$$ $$1\ hour=3600\ …


2018 December(B05) Math Question 36

Word Problems

- % Concentration


Choice H

$$\frac{$2.4}{16}=$0.15\ /ounces$$ $$$0.15\times10=$1.5$$


2018 December(B05) Math Question 37

Graphing Properties

- Interpret Graphs or Figures


Choice D


Choice G

The denominator of any fraction …


2018 December(B05) Math Question 39

Statistics

- Mean, Median


Choice E

$$0.1\times3+0.7\times4+0.2\times5$$ $$=0.3+2.8+1=4.1$$


Choice K

Cannot be determined from the …


2018 December(B05) Math Question 41

Absolute Values

- Absolute Value Expressions


Choice B

$$\mid a-b-1 \mid \gt0$$ $$\Rightarrow …


Choice G

$$2\pi r=2\times3.14\times5=31.4$$ $$150-31.4=118.6$$ $$118.6\div4=29.65$$


Choice D

b05

$$3\times4=12$$ $$3\times2=6$$ $$2\times4=8$$ $$(12+6+8)\times2=52$$ $$52\times$0.01=$0.52$$


2018 December(B05) Math Question 44

Word Problems

- 1 Variable Equations


Choice F

$$Cans:0.05+0.03=$0.08$$ $$Bottles:0.1+0.02=$0.12$$ $$200($0.15-$0.08)+300($0.18-$0.12)$$ $$=200($0.07)+300($0.06)$$ $$=$14+$18=$32 …


2018 December(B05) Math Question 45

Word Problems

- Cost


Choice B

$$\frac{0.1}{0.18}\approx. 0.56$$


2018 December(B05) Math Question 46

Word Problems

- 2 Variable Addition


Choice F

The recycling center sold x …


2018 December(B05) Math Question 47

Quadratic Equations

- FOIL


Choice D

$$x^{2}+mx+c=(x+2)(x+4)$$ $$=x^{2}+2x+4x+8$$ $$=x^{2}+6x+8$$ $$\Rightarrow m=6,\ …


2018 December(B05) Math Question 48

Trigonometry

- Graphing Trig Functions


Choice G

b05


2018 December(B05) Math Question 49

Conics

- Circles


Choice A

b05

$$Small\ circle\ :\ Large\ circle$$ …


Choice J

$$\frac{2a}{b}+\frac{b}{2a}$$ $$=\frac{2a\times2a}{b\times2a}+\frac{b\times b}{2a\times b}$$ $$=\frac{4a^{2}+b^{2}}{2ab}$$


2018 December(B05) Math Question 51

Graphing Properties

- Vectors


Choice B

b05


2018 December(B05) Math Question 52

Algebraic & Function Expressions

- Nested Functions


Choice G

$$f(g(x))=\sqrt[3]{x+1}-2$$ $$g(x)=x+1$$ $$f(x)=\sqrt[3]{x}-2$$ $$g(f(x))=(\sqrt[3]{x}-2)+1=\sqrt[3]{x}-1$$


2018 December(B05) Math Question 53

Sequences and Patterns

- Logical Expressions


Choice A

b05


Choice J

$$x^{\frac{4}{6}}\cdot x^{\frac{4}{3}}$$ $$=x^{\frac{4}{6}}\cdot x^{\frac{8}{6}}$$ $$=x^{\frac{4}{6}+\frac{8}{6}}$$ …


Choice A

$$\frac{3}{2}:\frac{2.5}{1.5}$$ $$=\frac{3}{2}:\frac{25}{15}$$ $$=\frac{3}{2}:\frac{5}{3}$$ $$=\frac{3}{2}\times\frac{3}{5}$$ $$=\frac{9}{10}$$


2018 December(B05) Math Question 56

Probability

- One Event


Choice J

$$P(Blue\ Cards)+P(17)-P(Blue\ 17)$$ $$=\frac{20}{100}+\frac{1}{20}-\frac{1}{100}$$ $$=\frac{20}{100}+\frac{5}{100}-\frac{1}{100}$$ …


Choice C

$$City's population:\ x$$ $$x\times1.2\times1.3\times0.8=1.248x$$ $$1.248x-x=0.248x$$


2018 December(B05) Math Question 58

Probability

- More than One Event


Choice K

b05

$$\Rightarrow\frac{1}{3}$$


2018 December(B05) Math Question 59

Trigonometry

- Pythagorean Theorem & sin cos tan


Choice A

b05

$$c^{2}=a^{2}+b^{2}-2ab\cos\angle C$$ $$\Rightarrow 10^{2}=x^{2}+14^{2}-2ab\cos\angle 34°$$


2018 December(B05) Math Question 60

Conics

- Ellipse


Choice F

b05