Toán Lớp 6: Tính tỉ số A/B biết : A = 4/7.31 + 6/7.41 + 9/10.41 + 7/10.57 và B = 7/19.31 + 5/19.43 + 3/23.43 + 11/23.57

Question

Toán Lớp 6:  Tính tỉ số A/B biết : A = 4/7.31 + 6/7.41 + 9/10.41 + 7/10.57   và B = 7/19.31 + 5/19.43 + 3/23.43 + 11/23.57

mytamhoang · Answer

Giải đáp:   A= 4/7.31 +6/7.41+9/10.41+7/10.57     =20/35.31+30/35.41+45/50.41+35/50.57     =5.(4/35.31+6/35.41+9/50.41+7/50.57)     =5(1/31&minus;1/35+1/35&minus;1/41+1/41&minus;1/50+1/50&minus;1/57)     =5(1/31&minus;1/57)     B=7/19.31+5/19.43+3/23.43+11/23.57     =14/34.31+10/38.43+6/46.43+22/46.57     =2.(7/34.31+5/38.43+3/46.43+11/46.57)     =2.(1/31&minus;1/34+1/34&minus;1/43+1/43&minus;1/46+1/46&minus;1/57)     =2.(1/31&minus;1/57)     A/B=[5.(1/31-1/57)] / [2.(1/31-1/57)]     A/B=5/2

khanhngantoan · Answer

~ Bạn tham khảo ~     Ta c&oacute; :    A = 4/[7.31] + 6/[7.41] + 9/[10.41] + 7/[10.57]   => A = 20/31.35+30/35.41+45/41.50+35/50.57   => A = 5(4/31.35+6/35.41+9/41.50+7/50.57)   => A = 5(1/31-1/35+1/35-1/41+1/41-1/50+1/50-1/57)   => A = 5(1/31-1/57) (1)    Lại c&oacute; :    B = 7/19.31 + 5/19.43 + 3/23.43 + 11/23.57   => B=14/38.31+10/38.43+6/46.43+22/46.57   => B = 2(7/31.38+5/38.43+3/43.46+11/46.57)   => B = 2(1/31-1/38+1/38-1/43+1/43-1/46+1/46-1/57)   => B = 2(1/31-1/57) (2)   Từ (1),(2) => A/B $=  dfrac{5 bigg( dfrac1{31}- dfrac1{57} bigg)}{5 bigg( dfrac1{31}- dfrac1{57} bigg)}= dfrac52$   Vậy A/B = 5/2