1
Review of Grade 5
Textbook, pp. 3–5
GoalReview natural numbers, common and decimal fractions and percentages from Grade 5; compute in a convenient way.
New words
convenient method (using properties) · qulay usuldecimal fraction · o‘nli kasrpercent (one hundredth) · foizproper fraction · to‘g‘ri kasr
Explanation
In Grade 5 you learned to work with natural numbers, common fractions, decimals and percentages. To make a calculation easier we use the distributive property: a · b + a · c = a · (b + c). A fraction whose numerator is smaller than its denominator is a proper fraction. One percent is one hundredth of a number: 1% = 1/100. To find a percentage of a number, divide the number by 100 and multiply by the percentage. These skills are the base for the new topics.
Worked examples
Compute 38 · 54 + 38 · 42 conveniently: take the common factor 38 out of the brackets, 38 · (54 + 42) = 38 · 96 = 3,648.
7/9 − 4/9 + 2/9: the denominators are equal, so we compute with the numerators: (7 − 4 + 2)/9 = 5/9.
Class activity
“Smart calculation contest”: the class splits into two teams. Examples such as 125 · 47 + 125 · 53 are written on the board. Team members come up in turn, explain the convenient method and write the answer. The team that is faster and correct scores a point.
Practice
1
Compute 125 · 47 + 125 · 53 in a convenient way.
12500
2
Find 20% of 150.
30
3
A rectangle's width is 4 m shorter than its length and its perimeter is 56 m. What is its area in m²?
192
4
Why is 3/8 a proper fraction but 8/3 is not?
In 3/8 the numerator (3) is smaller than the denominator (8). In 8/3 the numerator is bigger, so it is an improper fraction.