Math 6A, Lesson 14, Spring 2021, 5/23/2021

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1. No Quiz about percentage today

2. Discount

  • Discount = Marked price – Selling price
  • Percentage discount = ( Discount / Marked_price) x 100%
  • Selling price = (100% – Discount %) x Marked_price

3. Sales Tax and Income Tax

  • Tax = Tax_rate x Cost
  • Income_tax = Tax_rate x Income
  • Income: wage (hourly-paid), salary (annual basis)

4. Compound Discount

  • Each successive discount is based on the price after the previous discount

5. Points, Line and Planes

  • Point: has position; has no size
  • Line: has an infinite number of points; has no width; can be determined by two points; can be straight or curved
  • Ray: a part of a line with one endpoint
  • Endpoint
  • Line segment: a part of a line between two end points; has length
  • Plane: a flat surface; has no thickness
  • Parallel lines: two lines on the same plane do not intersect (meet or cut)
  • Perpendicular (lines) to each other: two lines intersect at right angle
  • Foot of the perpendicular

6. Types of angles

  • Acute angle: angle < 90 degree
  • Right angle: angle = 90 degree
  • Obtuse angle: 90 degree < angle < 180 degree
  • Reflex angle: 180 degree < angle < 360 degree

7. Complementary, supplementary, and adjacent angles

  • Complementary angles: the sum of two angles is 90 degree
  • Supplementary angles: the sum of two angels is 180 degree
  • Adjacent angles: two angles share a common side and a common vertex but do not overlap

8. Properties of Angles

  • The sum of adjacent angles on a straight line is 180 degree
  • The sum of all angles at a point is 360 degree
  • Vertically opposite angles: when two lines intersect, the vertically opposite angles are equal

9. Home Work:

  • Handout:
    • Three pages
  • Workbook:
    • Page 45: 1, 2, 3
    • Page 46: 4, 5
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