Đặt A = 11/12 + 19/20 + 29/30 + 41/42 + 55/56 + 71/72 + 89/90
A = 1 - 1/12 + 1 - 1/20 + 1 - 1/30 + 1 - 1/42 + 1 - 1/56 + 1 - 1/72 + 1 - 1/90
A = ( 1 + 1 + 1 + 1 + 1 + 1 + 1 ) - ( 1/12 + 1/20 + 1/30 + 1/42 + 1/56 + 1/72 + 1/90 )
A = 7 - 7/30
A = \(6\frac{23}{30}\)
Tính nhanh : a, 5/6 +11/12+19/20+29/30+41/42+55/56+71/72+89/90
b, ính tổng của 10 phân số trog phép cộng sau :
1/2 + 5/6+ 11/12 + 19/20 + 29/30 + 41/42 + 55/56 + 71/72 + 89/90 + 109/110
Tính nhanh:
a) 5/6+11/12+19/20+29/30+41/42+55/56+71/72+89/90
b) Tính tổng của 10 phân số trong phép cộng sau:
1/2+5/6+11/12+19/20+29/30+41/42+55/56+71/7289/90
Tính : A=1/2 + 5/6 + 11/12 + 19/20 + 29/30 + 41/42 + 55/56 + 71/72 + 89/90
Tính hợp lý: 1/2 + 5/6 +11/12 + 19/20 + 29/30 + 41/42 + 55/56 + 71/72 + 89/90
A=1/2+5/6+11/12+19/20+29/30+41/42+55/56+71/72+89/90
Tính nhanh
1/2+5/6+11/12+19/20+29/30+41/42+55/56+71/72+89/90
1/2+5/6+11/12+19/20+29/30+41/42+55/56+71/72+89/90 = ?
A=1/2+5/6+11/12+19/20+29/30+41/42+55/56+71/72+89/90
A=1/2+5/5+11/12+19/20+29/30+41/42+55/56+71/72+89/90 = ?
