標題:
數學問題(幫忙)(請用完整的步驟)
發問:
In a class of 45 students , the number of girl is more than the numbers of boys by 11. How many girls?How many boys? May buys some$2 and $5 stamps . If she spends $54 altogether and gets 15 stamps , how much does she buy ?
最佳解答:
Let the number of girls be x, x + x-11=45 x=28 There are 28 girls, 17boys Let number of $2 stamp be x, $5 stamp be y 2x +5y =54 (1) x+y=15 (2) put (2) into (1) 2(15-y) + 5y=54 3y= 24 y=8 so she buys 8 $5 stamps and 7 $2 stamps
First, presume girl is x, then, boy is 45-x from the question x-(45-x)=11(the number of girl is more than the numbers of boys by 11) x-45+x=11 2x=56 x=28 hence, girl is 28 and boy is 17 Second, presume $2 stamp is x, then, $5 is y x+y=15(..gets 15 stamps.. )(1) 2x+5y=54(..she spends $54 altogether ..)(2) from (1) y=15-x(join to(2)) 2x+5(15-x)=54 2x+75-5x=54 -3x=-21 x=7(join to (1)) 7+y=15 y=8 hence,May buys 7 $2 and 8 $5 stamps|||||Let the number of boy is X X+X+11=45 2X=34 X=17 SO the number of girl is 28 the numbers of boys is 17 Let May buy $2 stamps x,May buy $5 stamps y 2x+5y=54...1 x+y=15...2 2--y=15-x..3 2x+5(15-x)=54 2x+75-5x =54 -3x=-21 x=7 7+y=15 y=8 SO she buy $2 stamps 7, she buy $5 stamps 8|||||let x be the student of boys, 2x+11=45 2x=34 x=17 there are 17 boys in the class, there are 17+11=28 girls in the class. let y be the number of $5 stamp, 2*(15-y)+5y=54 30-2y+5y=54 3y=24 y=8 May buys 8 $5 stamps & 15-8=7 $2 stamps 2006-10-17 18:33:38 補充： 慢左=.=
數學問題(幫忙)(請用完整的步驟)
發問:
In a class of 45 students , the number of girl is more than the numbers of boys by 11. How many girls?How many boys? May buys some$2 and $5 stamps . If she spends $54 altogether and gets 15 stamps , how much does she buy ?
最佳解答:
Let the number of girls be x, x + x-11=45 x=28 There are 28 girls, 17boys Let number of $2 stamp be x, $5 stamp be y 2x +5y =54 (1) x+y=15 (2) put (2) into (1) 2(15-y) + 5y=54 3y= 24 y=8 so she buys 8 $5 stamps and 7 $2 stamps
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其他解答:First, presume girl is x, then, boy is 45-x from the question x-(45-x)=11(the number of girl is more than the numbers of boys by 11) x-45+x=11 2x=56 x=28 hence, girl is 28 and boy is 17 Second, presume $2 stamp is x, then, $5 is y x+y=15(..gets 15 stamps.. )(1) 2x+5y=54(..she spends $54 altogether ..)(2) from (1) y=15-x(join to(2)) 2x+5(15-x)=54 2x+75-5x=54 -3x=-21 x=7(join to (1)) 7+y=15 y=8 hence,May buys 7 $2 and 8 $5 stamps|||||Let the number of boy is X X+X+11=45 2X=34 X=17 SO the number of girl is 28 the numbers of boys is 17 Let May buy $2 stamps x,May buy $5 stamps y 2x+5y=54...1 x+y=15...2 2--y=15-x..3 2x+5(15-x)=54 2x+75-5x =54 -3x=-21 x=7 7+y=15 y=8 SO she buy $2 stamps 7, she buy $5 stamps 8|||||let x be the student of boys, 2x+11=45 2x=34 x=17 there are 17 boys in the class, there are 17+11=28 girls in the class. let y be the number of $5 stamp, 2*(15-y)+5y=54 30-2y+5y=54 3y=24 y=8 May buys 8 $5 stamps & 15-8=7 $2 stamps 2006-10-17 18:33:38 補充： 慢左=.=
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