8:00 GED Math Week 1 Tue

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Add, subtract, multiply, divide fractions

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8:00 GED Math Week 1 Tue

  1. 1. • 1. GED Practice (Writing Decimals as Fractions)• 2. Basic Review of fractions• 3. A/S/M/D Fractions
  2. 2. • At his job, Peter fills out a time sheet every Friday. This week, Peter spent 27.5 hours out of 40 hours, or 0.6875 of his time, working on Project A.• Which fraction is the best estimate of the time Peter spent on Project A? “seven tenths”(1) 2/3(2) 3/4(3) 3/10(4) 7/10(5) 7/25
  3. 3. • Summary: – Divide the denominator into the numerator – Write the remainder as a fraction•Example 1: Change to a mixed number. 4•Step 1: Divide 3 into 14. 3) 14 - 12 2•Step 2: Write the remainder (2) over the divisor(3) to form the fraction part of the answer.
  4. 4. •Example 2: Change to a mixed number. 1•Step 1: Divide 8 into 12. 8) 12 - 8 4•Step 2: Write the remainder (4) over the divisor(8) to form the fraction part of the answer.•Step 3: Reduce the fraction
  5. 5. • Summary: – Multiply the whole number by the denominator – Add to the numerator – Place over the current denominator•Example 1: Change to an improper fraction.•Step 1: Multiply the whole number by thedenominator .•Step 2: Add the numerator to the product.• Step 3: Write the answer over the denominatorto form the fraction part of the answer.
  6. 6. • Summary: Reducing changes the numbers in a fraction, but it does not change the VALUE of a fraction. Example: ReduceTo reduce a fraction,you divide both the •Step 1: Dividenumerator and both 14 and 16denominator by a by a numbernumber that goesinto them both that goes evenlyevenly. into both of them.
  7. 7. • You will need to know how to set up fractions and reduce them.Example: John makes $800 a month. He pays $200 amonth to rent a room. What fraction of his income doesJohn pay for rent?• Step 1: Find the whole. Write it in the denominator.• Step 2: Find the part. Write it in the numerator.• Step 3: Reduce.
  8. 8. • Summary: Reducing changes the numbers in a fraction, but it does not change the VALUE of a fraction.•Step 1: Divide Example: Reduceboth 30 and 45by a numberthat goes evenlyinto both ofthem.
  9. 9. • Summary: Later when you add and subtract fractions, you will often need to raise fractions to higher terms. This is the opposite of reducing.Example: Raise the fraction to higher terms byfinding the missing numerator.•Step 1: Divide the 4new numerator by the 6) 24old denominator.•Step 2: Multiply boththe old denominatorand numerator by 4.
  10. 10. • Summary: To compare fractions, you must have the same denominators. Raise each fraction to higher terms, then the new compare numerators.Example: Which fraction is bigger,•Step 1: Find acommon denominator ×7 21for 5 and 7 and raise to 7higher terms. ×7 5) 35•Step 2: Look at thenumerators anddecide which one is ×5 25 5 ×5 7) 35bigger.
  11. 11. • Step 1: Look at the denominators. If they are different, find a common denominator for the two x4 7 8 numbers. x4• Step 2: Rewrite the problem with new common denominators.• Step 3: Rewrite the numerators.• Step 4: Add the numerators.• Step 5: Reduce answer to lowest terms.
  12. 12. •Step 1: Find the Lowest ×3Common Denominator 21•Step 2: Add numerators ×3 ×8 16•Step 3: Change theimproper fraction to amixed number ×8•Step 4: Add the whole -24 13number part of theanswer to the mixed number.
  13. 13. Step 1: Find a common denominator. Step 2: Since you×3 8 6 cannot take 7 from 6, you must borrow ONE from the whole×3 number and add it to the fraction. Step 3: Subtract the numerators, keep the denominator. Step 4: Subtract the whole numbers.
  14. 14. • Step 1: Multiply the numerators together• Step 2: Multiply the denominators together.• Step 3: Reduce the answer if possible. 21  80
  15. 15. • To cancel, find a number that divides evenly into the numerator of one fraction and the denominator of the other.1 2 •Step 1: Divide 3 and 15 by 3 2 •Step 2: Divide 4 and 8 by 4 •Step 3: Multiply the new1 5 5 numerators and denominators.
  16. 16. • A whole number can be written as a fraction with a denominator of 1. • Remember: a fraction of means to multiply. Find ¾ of 24.•Step 1: Write 24 as a fraction.•Step 2: Divide 4 and 24 by 4.•Step 3: Multiply across.•Step 4: Change the improper fraction to a whole number.
  17. 17. • Step 1: Change to an improper fraction.• Step 2: Divide 4 and 6 by 2.• Step 3: Multiply across.• Step 4: Change the improper fraction to a mixed number.
  18. 18. • In division problems with fractions or mixed numbers, you must invert the divisor. The fraction ½ is the reciprocal, or the inverse of the improper fraction 2/1.
  19. 19. • Step 1: Write each number in fraction form.• Step 2: Invert the divisor and change the to a sign. (KSF!)• Step 3: Follow the rules for multiplying fractions.
  20. 20. • Change to an improper fraction and then proceed as usual.

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