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For more information, please see full course syllabus of Pre Algebra

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 0 answersPost by America Moctezuma on October 10, 2013This is my favirote lesson! 1 answerLast reply by: Professor FungSat Jul 20, 2013 1:49 AMPost by James Reynolds on July 17, 2013UpdateYour all those things and125% 0f 75 = 93.75, not 90I made the mistake of calculating for 70% instead of 75%.Apologies 0 answersPost by James Reynolds on July 17, 2013Hello N FungI'm really liking the lessons, they're helping me progress at a fast and steady pace whenever I like. You're really good on camera and have a calm and soothing voice that's great to listen to whilst learning.125% of 75 = 90, not 93.75Best Regards,

### Finding a Percent of a Number

• To find 10% of a number, move the decimal one place to the left.
• You can find 15% or 20% of a number, for tips, by finding 10% as a base.
• Remember to check if your answer makes sense. A percent over 100 is larger than the number. A percent smaller than the number is only a portion of the number.
• These are common fractions, percents, and decimals to remember.
•  Percent 5% 10% 20% 25% 50% 75% 100% Fraction 5/100 = 1⁄20 10/100 = 1⁄10 20/100 = 1⁄5 25/100 = 1⁄4 50/100 = 1⁄2 75/100 = 3⁄4 100/100 = 1 Decimal 0.05 0.1 0.2 0.25 0.5 0.75 1

### Finding a Percent of a Number

Find 26% of 150.
• 26% ×150 =
• 0.26 ×150 =
39
Find 75% of 93
• 75% ×93 =
• 0.75 ×93 =
69.75
Find 5% of 35.
• 5% ×35 =
• 0.05 ×35 =
1.75
Find 56% of 73.
• 56% ×73 =
• 0.56 ×73 =
40.88
Find 175% of 30.
• 175% ×30 =
• 1.75 ×30 =
52.5
Find 204% of 22.
• 204% ×22 =
• 2.04 ×22 =
44.88
Find 110% of 200
• 110% ×200 =
• 1.10 ×200 =
220
The bill at a restaurant is \$ 18.25. Estimate the amount of tip to leave if you want to tip 10%.
• Find 10% of \$ 18.25 by moving the decimal point one space to the left.
• 10% ×18.25 = 1.825
\$ 1.83
The bill at a restaurant is \$ 45.60. Estimate the amount of tip to leave if you want to tip 15%.
• First, find 10% of \$ 45.60 by moving the decimal point one space to the left.
• 10% ×45.60 = 4.56
• Half of 10% is 5% , so find half of 4.56 to find the 5% value.
• [1/2] ×4.56 = 2.28
• Finally, add the 10% value and 5% value together to find the 15% value.
• 4.56 + 2.28 =
\$ 6.84
The bill at a restaurant is \$ 27.83. Estimate the amount of tip to leave if you want to tip 20%.
• First, find 10% of \$ 27.83 by moving the decimal point one space to the left.
• 10% ×27.83 = 2.783
• Since 20% is two times 10% , double 2.783 to find the 20% value.
• 2.783 ×2 =
• 5.566
\$ 5.57

*These practice questions are only helpful when you work on them offline on a piece of paper and then use the solution steps function to check your answer.

### Finding a Percent of a Number

Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.

• Intro 0:00
• What You'll Learn and Why 0:05
• Topics Overview
• Vocabulary 0:20
• Percent
• Finding a Percent 0:26
• Example: Find 15% of 100
• Example: Find 10% of 135
• Finding More Percents 2:23
• Example: Find 8% of 65
• Example: Find 120% of 50
• Estimating a Percent 3:25
• Example: Estimate 10% of 31.05
• Example: Estimate 15% of 31.05
• Example: Estimate 20% of 31.05
• Extra Example 1: Find 7% of 120 5:35
• Extra Example 2: Find 125% of 75 6:01
• Extra Example 3: Estimate 15% Tip 7:02
• Extra Example 4: Estimate 20% Tip 8:01