Ta có 1/11; 1/12; 1/13;...; 1/39 > 1/40
\(\Rightarrow\) A = 1/11 + 1/12 + 1/13 +...+ 1/39 +1/40 > 1/40 + 1/40 + 1/40 +...+ 1/40 + 1/40(có 30 số hạng)
A > 30/40
Mà 30/40 =3/4 nên A >3/4
Vậy A > 3/4
mot nha may co 3 phan xuong . so cong nhan cua phan xuong 1 bang 36% tong so cong nhan nha may so cong nhan cua phan xuong 2 bang 3/5 so cong nhan cua phan xuong 3 . biet so cong nhan cua phan xuong 3 hon so cong nhan cua phan xuong 1 la 18 nguoi . tinh so nguoi moi phan xuong
Mot xi nghiep co 2 phan xuong. So cong nhan o phan xuong thu nhat bang 2/5 so cong nhan phan xuong thu hai . Cuoi nam co 22 cong nhan chuyen tu phan xuong 2 sang phan xuong 1 nen so cong nhan phan xuong 1 bang 5/7 so cong nhan phan xuong 2 tinh so cong nhan moi phan xuong ?
3 phan 1 nhan 4 cong 3 phan 4 nhan 7 cong 3 phan 7 nhan 10 cong ... cong 3 phan 40 nhan 43
1 phan 5 nhan 8 cong 1 phan 8 nhan 11 cong 1 phan 11 nhan 14 +..........+1 phan x nhan (x+3)=101 phan 1540
Tim phan so toi gian a/b biet :
a) Cong tu voi 4, cong mau voi 10 thi gia tri phan so ko doi
b) Cong mau vao tu, cong mau vao mau cua phan so thi duoc phan so moi bang 2 lan phan so da cho.
1) Tính:
a) A = 7 mu 2 phan 2 nhan 9 cong 7 mu 2 phan 9 nhan 16 cong 7 mu 2 phan 16 nhan 23 cong van van cong 7 mu 2 phan 65 nhan 72
tinh cac tong sau
a= 4 phan 3 nhan7 conh 4 phan 7 nhan 11 cong 4 phan 11 nhan 15cong chammm cong 4 phan 107 nhan 111
1 13 phan 15 nhan 0 phay 75 tru (11 phan 20 cong 25 phan tram ) chia 7 phan3
tim phan so toi gian a/b:cong mau vao tu ; cong mau vao mau thi duoc 1 phan o gap 2 lan phan so da cho
