\(B=1+2+4+5+7+8+10+...+119+121+122\)
Ta có :
\(A=1+2+3+...+121+122\)
\(A=\left[\left(122-1\right):1+1\right]\left(1+122\right):2\)
\(A=122.\left(123\right):2=7503\)
Ta lại có :
\(C=3+6+9+...+120\)
\(C=\left[\left(120-3\right):3+1\right]\left(3+120\right):2\)
\(C=40.123:2=2460\)
Ta thấy : \(B=A-C\)
\(B=7503-2460=5043\)
tính nhanh:
B=1+2+4+5+7+8+10+...+119+121+122
C=1.2+2.3+3.4+...+58.59+59.60
chuyển thành phân số
a, 2 1/3 ; 4 2/5 ; 3 1/4 ; 9 5/7 ; 11 3/10
b, 5 2/17 ; 3 6 /23 ; 7 4/9 ; 121 15/100 ;8 3/7
vt cách trình bày đầy đủ
a, 5/11 + 1/2 + 2/5 + 6/11 + 3/4 + 16/25 + 5/16
b,19/4 + 37/100 + 1/8 + 132/25 + 5/2 + 37/12
c, 1313/1313 * 165165/143143 * 424242/151515
d, (121/122 * 123/125 + 127/129) * (1995/1996 * 17/16 - 21/25 : 16/17) * (42/30 * 75/23 - 19/23 * 210/38
3/5*8 + 3/8*11 + 3/11*14 +....+3/119*122
( x x 2 ) + ( x x 5 ) + ( x x 8 ) + ... + ( x x 119 ) = 121
Bài 1: Tính nhanh
a, 5/11 + 1/2 + 2/5 + 6/11 + 3/4 + 16/25 + 5/16
b,19/4 + 37/100 + 1/8 + 132/25 + 5/2 + 37/12
c, 1313/1313 * 165165/143143 * 424242/151515
d, (121/122 * 123/125 + 127/129) * (1995/1996 * 17/16 - 21/25 : 16/17) * (42/30 * 75/23 - 19/23 * 210/38)
b,19/4 + 37/100 + 1/8 + 132/25 + 5/2 + 37/12
c, 1313/1313 * 165165/143143 * 424242/151515
d, (121/122 * 123/125 + 127/129) * (1995/1996 * 17/16 - 21/25 : 16/17) * (42/30 * 75/23 - 19/23 * 210/38
( 3/10/99 + 4/11/119 - 5/8/299 ) * ( 1/2 -1/3 -1/6 ) =?
2*3*4*...*121*122*123
