Envision Math 2.0: Grade 8, Volume 1
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1. Rational Numbers as Decimals
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Exercise 19 Page 12

Find the fraction form of each repeating decimal.

Practice makes perfect

We will draw lines to connect each repeating decimal with an equivalent fraction. To do so we will find fraction form of each repeating decimal. Let's start with the first one.

To find the fraction form of 0.17 we will first represent the repeating decimal with the variable x. Then we will write an equation by setting this variable equal to 0.17. x=0.17Since 0.17 has two repeating digits, we will multiply both sides of the equation by 10^2.
x=0.17
x* 10^2=0.17* 10^2
x* 100=0.17* 100
100x=17.17
Next we will subtract x from both sides of the equation. Since x=0.17, we will substitute 0.17 for x on the right-hand side. Finally, we will solve the obtained equation for x.
100x=17.17
100x-x=17.17-x
100x-x=17.17 - 0.17
99x=17
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Solve for x
99x/99=17/99
99x/99=17/99
x=17/99
We found that x is equal to 1799. Remember that x is also equal to 0.17. By the Transitive Property of Equality, we can conclude that the fraction is equal to the given repeating decimal number. x= 0.17 x= 17/99 ⇒ 0.17= 17/99 With this information we can draw a line to connect the repeating decimal with the equivalent fraction.

We will follow the same steps to match the repeating decimals with their equivalent fraction forms.

Variable Equation Number of Repeating Digits (n) Multiply Equation by 10^n Subtract the Variable From the Equation Solve for the Variable Transitive Property of Equality
0.351 v v= 0.351 3 v * 10^3=0.351 * 10^3 1000v=351.351 1000v-v=351.351-v 1000v-v=351.351- 0.351 999v=351 v&=351/999 &=13/37 0.351=13/37
0.17 w w= 0.17 1 w * 10^1=0.17 * 10^1 10w=1.7 10w-w=1.7-w 10w-w=1.7- 0.17 9w=1.6 v&=1.6/9 &=16/90=8/45 0.17=8/45
0.351 y y= 0.351 2 y * 10^2=0.351 * 10^2 100y=35.151 100y=35.151 100y-y=35.151- 0.351 99y=34.8 y&=34.8/99 &=348/990=58/165 0.351=58/165
0.351 z z= 0.351 1 z * 10^1=0.351 * 10^1 10z=3.511 10z-z=3.511-z 10z-z=3.511- 0.351 9z=3.16 y&=3.16/9 &=316/900=79/225 0.351=79/225

Finally, we will draw the lines that connect the repeating decimals with their fraction forms.