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S1 Math (Algebra)
發問:
1. An even number can be written as 2n , where n is an integer. a). Write down the even number which is just less than 2n. a). Write down the even number which is just greater than 2n.2.The sum of the the first n natural numbers is 1/2n(n+1). Find the sum of the first 12 natural numbers .3.A sum of... 顯示更多 1. An even number can be written as 2n , where n is an integer. a). Write down the even number which is just less than 2n. a). Write down the even number which is just greater than 2n. 2.The sum of the the first n natural numbers is 1/2n(n+1). Find the sum of the first 12 natural numbers . 3.A sum of $830 was distributed among 35 children , each child over 10 years age received $25 and those below 10 years got $16 each.How many children were over 10 years of age ?
最佳解答:
其他解答:
1a) 2n-2 = 2(n-1) 1b) 2n+2 = 2(n+1) 2) sub n = 12, ans = (1/2)(12)(12+1) = 78 3) let number of child over 10 years of age be x let number of child below 10 years of age be y x+y = 35 ----------------- (E1) 25x+16y = 830 ------- (E2) 25*(E1) - (E2) : 25x+25y-25x-16y = 25*35-830 9y = 45 y = 5 x = 35-5 = 30 So there are 30 children over 10 years of age
S1 Math (Algebra)
發問:
1. An even number can be written as 2n , where n is an integer. a). Write down the even number which is just less than 2n. a). Write down the even number which is just greater than 2n.2.The sum of the the first n natural numbers is 1/2n(n+1). Find the sum of the first 12 natural numbers .3.A sum of... 顯示更多 1. An even number can be written as 2n , where n is an integer. a). Write down the even number which is just less than 2n. a). Write down the even number which is just greater than 2n. 2.The sum of the the first n natural numbers is 1/2n(n+1). Find the sum of the first 12 natural numbers . 3.A sum of $830 was distributed among 35 children , each child over 10 years age received $25 and those below 10 years got $16 each.How many children were over 10 years of age ?
最佳解答:
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1. An even number can be written as 2n , where n is an integer. a). Write down the even number which is just less than 2n. as 2n is an even number the even number which is just less than 2n must be 2n - 2 b). Write down the even number which is just greater than 2n. as 2n is an even number the even number which is just less than 2n must be 2n + 2 2) The sum of the the first n natural numbers is 1/2n(n+1). Find the sum of the first 12 natural numbers . as The sum of the the first n natural numbers is 1/2n(n+1) when n = 12 The sum of the the first n natural numbers = the sum of the first 12 natural numbers = 1/2(12)(12+1) = 78 3)A sum of $830 was distributed among 35 children , each child over 10 years age received $25 and those below 10 years got $16 each.How many children were over 10 years of age ? Let the number of children over 10 years of age be x then the number of children below 10 years = 35 - x so 830 = 25 * (35-x) + 16*x 830 = 875 - 25x + 16x 9x = 45 x = 5 so there were 10 children over 10 years of age 希望幫到你 2007-12-27 14:15:37 補充： 唔好意思~發現第三題掉轉左黎計Let the number of children over 10 years of age be xthen the number of children below 10 years = 35 - xso 830 = 25 * x + 16*(35-x)830 = 25x + 560 - 16x9x = 270x = 30so there were 30 children over 10 years of age其他解答:
1a) 2n-2 = 2(n-1) 1b) 2n+2 = 2(n+1) 2) sub n = 12, ans = (1/2)(12)(12+1) = 78 3) let number of child over 10 years of age be x let number of child below 10 years of age be y x+y = 35 ----------------- (E1) 25x+16y = 830 ------- (E2) 25*(E1) - (E2) : 25x+25y-25x-16y = 25*35-830 9y = 45 y = 5 x = 35-5 = 30 So there are 30 children over 10 years of age
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