ISEE Lower Level Quantitative : How to find the solution to an equation

Study concepts, example questions & explanations for ISEE Lower Level Quantitative

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Example Questions

Example Question #51 : How To Find The Solution To An Equation

What is the value of the expression?

\displaystyle (5+3) * 2 

Possible Answers:

\displaystyle 17

\displaystyle 8

\displaystyle 11

\displaystyle 16

\displaystyle 12

Correct answer:

\displaystyle 16

Explanation:

First you add what is inside the parentheses. 

\displaystyle 5+3=8.

Then, we multiply, 

\displaystyle 8*2.

This leaves us with our answer of 16.

Example Question #52 : How To Find The Solution To An Equation

A pencil costs $1.03 and Elena wants to purchase 386 pencils. Which expression gives the best estimate of the total cost of Alex's purchase in dollars?

Possible Answers:

\displaystyle 130*400

\displaystyle 1*400

\displaystyle 1*40

\displaystyle 10*380

\displaystyle 130*100

Correct answer:

\displaystyle 1*400

Explanation:

To solve, we round $1.03 to $1.00 and round 386 pencils to 400.

Then we would multiply to find the answer, so \displaystyle 1*400 would give us the best estimate.

Example Question #53 : How To Find The Solution To An Equation

Find the value of the expression. 

\displaystyle (8-6)/2

Possible Answers:

\displaystyle 0

\displaystyle 2

\displaystyle 7

\displaystyle 1

\displaystyle 3

Correct answer:

\displaystyle 1

Explanation:

To solve the expression, you must first solve inside the parentheses, so 

\displaystyle 8-6=2.

Then we divide 2 by 2 and are left with our answer, 1.

Example Question #54 : Algebraic Concepts

Caitlin received \displaystyle \small x tickets to a concert for Friday night. She divides them equally among herself and her four friends. Which of the following expressions shows the number of tickets each person received?

Possible Answers:

\displaystyle x-4

\displaystyle x-5

\displaystyle \frac{x}{4}

\displaystyle \frac{x}{5}

\displaystyle x\cdot 5

Correct answer:

\displaystyle \frac{x}{5}

Explanation:

Including Caitlin, there are 5 total people receiving tickets.

If she is going to divide them among her friends, then we would use division,

\displaystyle \frac{\text{Number of Tickets}}{\text{Number of People}}=\frac{x}{5}

Example Question #55 : Algebraic Concepts

Solve for \displaystyle \small x.  

\displaystyle \small 4x+2x-x=15

Possible Answers:

\displaystyle \small x=3

\displaystyle \small x=5

\displaystyle \small x=4

\displaystyle \small x=1

\displaystyle \small x=2

Correct answer:

\displaystyle \small x=3

Explanation:

First we add and are left with 

\displaystyle \small 6x-x=15.

Then we subtract and are left with 

\displaystyle \small 5x=15.

Finally, in order to get the \displaystyle \small x alone, we divide each side by 5 and are left with 

\displaystyle \small x=3.

Example Question #56 : Algebraic Concepts

Solve for \displaystyle \small x.

\displaystyle \small \small 1+3+(8-2)*2=x

Possible Answers:

\displaystyle \small x=16

\displaystyle \small x=13

\displaystyle \small x=20

\displaystyle \small x=12

\displaystyle \small x=19

Correct answer:

\displaystyle \small x=16

Explanation:

Following the order of operations, we must do the work inside the parentheses first, so we are left with 

\displaystyle \small 1+3+6*2=x.

Then we must multiply and are left with 

\displaystyle \small 1+3+12=x.

Finally 

\displaystyle \small 4+12=x.

So 

\displaystyle \small x=16.

Example Question #57 : How To Find The Solution To An Equation

Five more than a number is equal to \displaystyle \frac{3}{5} of twenty-five . What is the number?

Possible Answers:

\displaystyle 20

\displaystyle 30

\displaystyle 15

\displaystyle 25

\displaystyle 10

Correct answer:

\displaystyle 10

Explanation:

From the question, we know that \displaystyle 5 plus a number equals \displaystyle \frac{3}{5} of \displaystyle 25. In order to find out what \displaystyle \frac{3}{5} of \displaystyle 25 is, multiply \displaystyle \frac{3}{5} by \displaystyle \frac{25}{1}.  

 

\displaystyle \frac{3}{5}\times\frac{25}{1}=\frac{75}{5}, or \displaystyle 15.

The number we are looking for needs to be five less than \displaystyle 15, or \displaystyle 10.

You can also solve this algebraically by setting up this equation and solving:

\displaystyle 5+x=\frac{3}{5}\times25

\displaystyle 5+x=15 

Subtract \displaystyle 5 from both sides of the equation.         

\displaystyle x=10

 

Example Question #57 : Algebraic Concepts

Solve for \displaystyle x:

\displaystyle 14x - 6=64

Possible Answers:

\displaystyle 4

\displaystyle 6

\displaystyle 3

\displaystyle 5

Correct answer:

\displaystyle 5

Explanation:

To solve an equation, first combine like terms. Move the \displaystyle -6 over to the other side of the equation by adding \displaystyle +6:

\displaystyle 14x - 6=64

         \displaystyle +6=+6

        \displaystyle 14x=70

Next, remove the \displaystyle 14 from the variable by dividing by \displaystyle 14.

\displaystyle \frac{14x}{14}=\frac{70}{14}\rightarrow x=5

The answer is \displaystyle 5.

Example Question #61 : How To Find A Ratio

At a local market, farmers trade produce to obtain a more diverse crop. A farmer will trade \displaystyle 13 turnips for \displaystyle 3 ears of corn. If a man has \displaystyle 9 ears of corn, then how many turnips can he get?

Possible Answers:

\displaystyle 43\ \text{turnips}

\displaystyle 93\ \text{turnips}

\displaystyle 39\ \text{turnips}

\displaystyle 22\ \text{turnips}

\displaystyle 94\ \text{turnips}

Correct answer:

\displaystyle 39\ \text{turnips}

Explanation:

Ratios can be written in the following format:

\displaystyle A:B\rightarrow \frac{A}{B}

Using this format, substitute the given information to create a ratio.

\displaystyle 3\ \text{corn}: 13\ \text{turnips}

Rewrite the ratio as a fraction.

\displaystyle 3\ \text{corn}: 13\ \text{turnips}\rightarrow \frac{3\ \text{corn}}{13\ \text{turnips}}

We know that the farmer has \displaystyle 9 ears of corn. Create a ratio with the variable \displaystyle T that represents how many turnips he can get.

\displaystyle \frac{9\ \text{corn}}{T}

Create a proportion using the two ratios.

\displaystyle \frac{3\ \text{corn}}{13\ \text{turnips}}=\frac{9\ \text{corn}}{T}

Cross multiply and solve for \displaystyle T.

\displaystyle 9\ \text{corn}\times 13\ \text{turnips}=3\ \text{corn}\times T

Simplify.

\displaystyle 3T=117

Divide both sides of the equation by \displaystyle 3.

\displaystyle \frac{3T}{3}=\frac{117}{3}

Solve.

\displaystyle T=39

The farmer can get \displaystyle 39\ \text{turnips}.

Example Question #54 : How To Find The Solution To An Equation

At a local market, farmers trade produce to obtain a more diverse crop. A farmer will trade \displaystyle 13 turnips for \displaystyle 3 ears of corn. If a man has \displaystyle 27 ears of corn, then how many turnips can he get?

Possible Answers:

\displaystyle 111\ \text{turnips}

\displaystyle 171\ \text{turnips}

\displaystyle 127\ \text{turnips}

\displaystyle 117\ \text{turnips}

\displaystyle 87\ \text{turnips}

Correct answer:

\displaystyle 117\ \text{turnips}

Explanation:

Ratios can be written in the following format:

\displaystyle A:B\rightarrow \frac{A}{B}

Using this format, substitute the given information to create a ratio.

\displaystyle 3\ \text{corn}: 13\ \text{turnips}

Rewrite the ratio as a fraction.

\displaystyle 3\ \text{corn}: 13\ \text{turnips}\rightarrow \frac{3\ \text{corn}}{13\ \text{turnips}}

We know that the farmer has \displaystyle 27 ears of corn. Create a ratio with the variable \displaystyle T that represents how many turnips he can get.

\displaystyle \frac{27\ \text{corn}}{T}

Create a proportion using the two ratios.

\displaystyle \frac{3\ \text{corn}}{13\ \text{turnips}}=\frac{27\ \text{corn}}{T}

Cross multiply and solve for \displaystyle T.

\displaystyle 27\ \text{corn}\times 13\ \text{turnips}=3\ \text{corn}\times T

Simplify.

\displaystyle 3T=351

Divide both sides of the equation by \displaystyle 3.

\displaystyle \frac{3T}{3}=\frac{351}{3}

Solve.

\displaystyle T=117

The farmer can get \displaystyle 117\ \text{turnips}.

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