VIEWS: 15 PAGES: 38 POSTED ON: 5/6/2010
L.O.1 To recall multiplication facts up to 10 x 10 Don’t draw the table just write the missing answers in order in your book. X 5 7 3 9 4 2 8 6 5 25 40 6 18 7 28 4 24 9 18 2 ½ minutes Which multiplication facts are hard to remember? Why do you think that is? Which are easy to remember? L.O.2 To understand area measured in square centimetres To begin to understand the formula “length x breadth” for the area of a rectangle What do we mean by the word “area”? Show where the area of your table top is. REMEMBER… The area of a 2-D shape is the amount of surface within its perimeter. Q. How can we work out the area of this rectangle? We can do it by counting the squares. The rectangle has 24 squares Its area can be written as 24 square centimetres or 24 cm². Draw 2 rectangles in your book. Write the dimensions and areas next to each. Be prepared to explain your working. Q. Is there a quick way to find the area of a rectangle? You should find that multiplying the number of squares in each row by the number in each column gives the area. These numbers are equivalent to the length and the width / breadth. So the area of a rectangle can be written as length x breadth or length x width. Check this theory by drawing more rectangles: Prisms draw 6 Spheres 5 Tetrahedra 4 but consider…. Q. If you double the length of a rectangle what happens to its area? Q. What would happen to the area if you doubled the length and the width? This is a patio. Each paving slab measures 60cm by 60 cm. Q. If we had used 30cm by 30 cm. paving slabs would we have used twice as many? We would have used 4 times as many because we need 4 small slabs to cover each large one. Q. How can we find the area of this shape? 4 cm 6 cm A B 4 cm We can do it like this - by turning it into TWO shapes, inserting the missing dimensions then adding the two areas A and B. 4 cm 4 cm A 2 cm B or like this…… Use either method to work out the area of this shape then draw a similar shape but with dimensions half the size. Calculate the area of your new shape. . 2 cm 4 cm 1 cm 6 cm You should have something like this. Its area should be 10 cm² . Using this shape repeat what you’ve just done. You may need to make 3 areas this time. By the end of the lesson the children should be able to: Express the formula for the area of a rectangle first in words, then in letters. Choose a suitable unit to estimate the area. L.O.1 To be able to use doubling to multiply two-digit numbers by 4. To halve any two-digit number. We are going to double these numbers: 63 18 47 52 66 39 56 27 98 77 95 41 We are going to halve these numbers: 64 78 20 52 48 66 42 74 32 50 96 22 If we halve these numbers how can we express the answers? Will they be fractions or decimals? 23 87 65 93 31 47 59 75 19 24 Q. What is a quick way to multiply this number by 4? Doubling twice is the quick mental method to multiply by four. We’ll multiply each of these aloud by 4. 23 55 34 18 87 76 39 L.O.2 To be able to understand area measured in square centimetres. To understand and use the formula in words “length x breadth” for the area of a rectangle. cm² We used cm² to find the areas of shapes in yesterday’s lesson. Here we have a square metre. 1metre How many cm² are there in I square metre? 1metre 1m² How can we work it out? 1m² = 10 000cm² because length = 100cm. and breadth = 100cm. and 100cm x 100cm = 10 000cm² 1mm² Try to imagine a millimetre square Q. How many mm² are there in 1cm²? Q. How can we work it out? 1cm² = 100mm² because length = 10mm and breadth = 10mm and 10cm x 10 cm = 100mm² Which of the three units ( m² ,cm² , or mm²) would be best for measuring these? 1. The classroom floor. 2. An exercise book. 3. A postage stamp. 4. The playground. 5. A chocolate bar wrapper. 6. A mouse mat. 7. Your thumbnail. . 2.8 cm 6.1 cm The area of a rectangle is length x breadth or l x b for short. Here the area would be 6.1 x 2.8 but it is useful first to get an ESTIMATE Q. What is the approximate area of the rectangle? . 2.8 cm 6.1 cm Rounding UP and DOWN leads to an approximate area of 6 x 3 = 18cm² Let’s try with these: 1. 1.7cm 5.9 cm Rounding UP and DOWN leads to 6cm x 2 cm = 12cm² 2. 3.2cm 11.8cm Rounding UP and DOWN leads to 12cm x 3 cm = 36cm² . With a partner complete Activity Sheet 7.1 . In which rectangles do you think the area has been underestimated? Using calculators we’ll check your estimates but will round part-answers to the nearest whole number. Q. What areas of shapes in the classroom would you measure in mm², cm², or m²? Record about a dozen altogether. In your book draw rectangles using cm and mm and write their length and breadth. Be accurate! Your partner must first estimate the area by rounding up or down then work out the area to the nearest whole number using a calculator. Record both the estimate and the final answer. Tetrahedra draw 2 Spheres draw 3 Prisms draw 4 Extension: measure area to two decimal points. By the end of the lesson children should be able to: Express the formula for the area of a rectangle first in words then in letters. Choose a suitable unit to estimate the area.