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Tham khảo tài liệu 'symbols of addition 8', ngoại ngữ, anh ngữ phổ thông phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | THEA MATH REVIEW Reciprocal Rules There are special rules for the sum and difference of reciprocals. The reciprocal of 3 is 3 and the reciprocal of x is 1 x If x and y are not 0 then x I y Yy E x. If x and y are not 0 then Y - y x - x y xy . Translating Words into Numbers The most important skill needed for word problems is being able to translate words into mathematical operations. The following will be helpful in achieving this goal by providing common examples of English phrases and their mathematical equivalents. Phrases meaning addition increased by sum of more than exceeds by. Examples A number increased by five x 5. The sum of two numbers x y. Ten more than a number x 10. Phrases meaning subtraction decreased by difference of less than diminished by. Examples 10 less than a number x - 10. The difference of two numbers x - y. Phrases meaning multiplication times times the sum difference product of. Examples Three times a number 3x. Twenty percent of 50 20 X 50. Five times the sum of a number and three 5 x 3 . Phrases meaning equals is result is. Examples 15 is 14 plus 1 15 14 1. 10 more than 2 times a number is 15 2x 10 15. 125 ---------------------------------- THEA MATH REVIEW -------------------------------------- Assigning Variables in Word Problems It may be necessary to create and assign variables in a word problem. To do this first identify any knowns and unknowns. The known may not be a specific numerical value but the problem should indicate something about its value. Then let x represent the unknown you know the least about. Examples Max has worked for three more years than Ricky. Unknown Ricky s work experience x Known Max s experience is three more years x 3 Heidi made twice as many sales as Rebecca. Unknown number of sales Rebecca made x Known number of sales Heidi made is twice Rebecca s amount 2x There are six less than four times the number of pens than pencils. Unknown the number of pencils x Known the number of pens 4x - 6 Todd has assembled
