MATH 4

GRADE IV CONGRUENT ANGLESObjective: Identify congruent angles.REVIEWLook at the illustration below. Name at least 5 right angles, 5 acute angles and 5obtuse angles.AB CD JIKHG FE If you are able to give the names of the different angles you may now continuewith this lesson. If not, review your lesson with the different kinds of angles. In this lesson, you are going to learn how to identify congruent angles. Makesure that you pay attention to the illustrations and the explanations. Do your best! 1

STUDY AND LEARN XA. A B CY Z Look at angle ABC and angle XYZ. Measure their angles using a protractor.Do they have the same measure? How many degrees does each angle have? If theirmeasures are both 90, they are congruent. All right angles are congruent sincethey all measure 90. We write it this way: ABC  XYZ. We read it, ABC iscongruent to angle XYZ.B. Try these two angles. XPOZ ML Measure each angle by a protractor. Are the measures of XOZ and PLMequal? If the measures of two angles are equal, the two angles are congruent. Inthe above example, we say XOZ is congruent to PLM. We write it this wayXOZ  PLM. 2

TRY THESEHere are different angles. Measure each angle to be able to identify which angles arecongruent. A L AY BC A A C DO T T B F T O T TET T 3

WRAP UP Two angles are said to be congruent if their measuresare the same. ON YOUR OWNName at least two pairs of angles that are congruent in each figure.1. A B 2. X Z O W YDC3. A V B D E C 4

GRADE IV KINDS OF PLANE FIGURES Objective: Identify the different kinds of plane figures. REVIEWHave you gone to the city? Or, have you read stories about the life in the city? Readthis story. Lucia and Gary went to visit their uncle and cousins in the city. When they arrived at the city proper, they saw signs like the following: STOP SCHOOLCROSSING ONE WAY BUS STOP Can you name the shapes of the different signboards they have seen? Do the shapes have meanings? Is there a need to have some signboards on the street? Why? Do we need to follow these signs? 1

STUDY AND LEARNLook at the plane figures below. Count the sides each figure has. rhombus parallelogram square trapezoid rectangletriangles quadrilateralpentagon hexagon heptagon octagonnonagon decagon circle The figures above are called plane figures because they have no thickness. A plane is amathematical term for a flat surface and takes any of the geometric plane shapes like a circle orany in the family of simple closed shapes made up of segments called polygons. A polygon is a closed plane figure formed by line segments. If polygons are closed plane figures, what could be the least number of lines thatdetermine a polygon? 2

Polygons are named according to the number of sides or angles they have. The number ofsides is equal to the number of angles. Triangles have three sides. Quadrilaterals ( square,rectangle, rhombus, parallelogram, trapezoid) have four sides. Pentagons have five sides. How many sides does a nonagon have? How about octagon? How about a circle? How many sides does it have? Is it a polygon? TRY THESE Write A inside the figure with 3 sides, B inside the figure with no sides, C inside the figure with 4 sides and D with more than 4 sides. 3

WRAP UP Plane figures are figures that have no thickness. They include the geometric plane shapes like a circle or any in the family of simple closed shapes made up of segments called polygons. ON YOUR OWNIdentify the different figures and count how many. 4

GRADE IV PERIMETER OF A SQUARE OR A RECTANGLE Objective: Find the perimeter of a square and a rectangle.REVIEWMatch the name with the correct figure. Write the letter of your answer in your paper.1. hexagon AB2. quadrilateral3. octagon CD4. pentagon EF5. triangle Check your answers with the answer key. If you get 4 or 5, you may continuewith the lesson. If not, review the different kinds of polygons. STUDY AND LEARNRead the given situation then decide what you are going to do. Your EPP teacher told the groups to put a red ribbon around the white handkerchief.You want to know how long is the piece of ribbon that you are going to use. 1

The diagram shows the dimensions of the handkerchief. 25 cm25 cm 25 cm 25 cmAnswer the following: 1. What are you asked to find? perimeter of the handkerchief. 2. What is the shape of the handkerchief? square 3. What are given? all the sides measuring 25 cm 4. How are you going to find the answer? Add all the measurements of the sides 5. What is the perimeter of the handkerchief? Show your solution. 25 cm + 25 cm + 25 cm + 25 cm = 100 cm 6. Is there another way of solving the problem? What is it? Yes, 4 x 25 cm = 100 cm 7. Where did we get 4? the four equal sides of the square 8. How about 25 cm? the length of one side of a square 9. What is the shorter way of finding the perimeter of a square? Perimeter of a square = 4 x side or P =4S 2

Now, let’s find out if there is also another way of finding the perimeter of arectangle. Study the drawing very well. 30 m24 m 24 m 30 m1. How long is the rectangle? 30 m What can you say about its length? equal2. How wide is it? 24 m What can you say about its width? equal3. What is the perimeter? Show your solution. P = 24 m + 24 m + 30 m + 30 m = 108 m4. Is there another way of finding the perimeter of the rectangle? Yes, P = 2l + 2w5. What is the perimeter of the handkerchief? Show your solution. P = 2l + 2w or P = 2 (l + w) = 2(30) + 2(24) = 60 + 48 = 108 m 3