Examples: Multiply (a) 65 by 99; (b) 58 by 98; (c) 27 by 19; (d) 64 by 101; (e) 38 by 21. WORK (a) 99X65=(100X65)-65-6500-65-6435, Ans. = (d) 101X64-6400+64-6464, Ans. (e) 21X38=(20X38)+38=760+38=798, Ans. Multiply, using short methods: a [Use pencil when needed] 1. 127 by 98 274 by 98 Examples: Multiply (a) 98 by 50; (b) 64 by 25; (c) 72 by 75; (d) 160 by 125; (e) 182 by 150; (f) 84 by 250; (g) 28 by 5; (h) 64 by 15; (i) 125 by 500; (j) 65 by 20. (a) 50X 98 (b) 25X 64 (c) 75X 72 (d) 125×160 WORK of 100X 98-4900, Ans. of 100X 72=5400; or, 7200-of 7200-5400, Ans. (e) 150X182=14x18,200=27,300, Ans. (f) 250× 84 of 1000×84=21,000, Ans. (g) 5X 28 of 10X28-140, Ans. (h) 15× 64-10×64+ of 10X64-960, Ans. = 5. Multiply 486 by 25; by 75; by 5; by 50; by 150; by 250; by 15; by 20; by 125; by 500. Examples: Multiply (a) 64 by 92; (b) 128 by ; (c) 56 by 87; (d) 140 by 37; (e) 246 by 331. WORK (a) 9× 64=(10X64)-(of 64)=640-16=624, Ans. 128-(of 128)=128-16-112, Ans. of 100X56-5600-of 5600-5600-700-4900, Ans. To divide a number by 10, move the decimal point one place to the left; to divide by 100, move the decimal point two places to the left, and so on. Thus, 87.÷10=8.7/=8.7 562.÷100=5.62/=5.62 Examples: Divide (a) 82 by 50; (b) 128 by 25; (c) 1754 by 250; (d) 1628 by 500; (e). 152 by 125; (f) 8200 by .33; (g) 8200 by 33; (h) 2100 by .87; () 2100 by 87. WORK (a) 82÷ 50=82÷(of 100)=2X.82=1.64, Ans. 8 (c) 1754÷ 250-1754÷1000-4×1.754=7.016, Ans. (i) 2100872100÷(100×3)=21X=24, Ans. Short Methods Games Prepare examples like the following, and play such games as Scaling the Ladder" or "Scaling the Wall," " "Baseball," "Obstacle Race," Mountain Climbing," etc. 99 66 Ask your teacher to arrange the class in rows or teams. The teacher or the captains of the teams may prepare the examples. The winning team is the one that has the greatest number of correct answers in the given time. 1. Scaling the Ladder. See who can climb to the top of the ladder most quickly. A wrong 2. Baseball. See which team scores the most runs. The class may be divided into two teams, A and B. When team A is at bat, each member must answer the question dictated by the teacher or some one else. Every correct answer is a "run." A wrong answer means that the team is "retired 99 and the other team then goes to bat. Keep the score by innings. The captains may prepare sets of examples like the following: 3. Obstacle Race. See who runs fastest. A wrong answer means a fall. The team having the greatest number of correct answers when time is called or when the race is over is the winning team. The teacher or |