1/1*2 + 1/2*3 + 1/3*4 .+ 1/49*50=?

1/1*2 + 1/2*3 + 1/3*4 .+ 1/49*50=?

Thinking:
Because (1 / 1 * 2) is (1-1 / 2)
(1 / 2 * 3) is (1-1 / 3)
.
According to this reasoning
The results are as follows
=1-1/2+1/2-1/3…… +1/49-1/50
=1-1/50
=49/50

Grade 6 mathematics volume 1 intelligence problems on page 70 of YiDianTong
A, B and C race, a is one tenth faster than B, C is one tenth slower than B, how much is the speed of a

Let B's speed be 10, a's 11, and C's 9
So the speed of a is 11 / 10, 11 / 10 of that of B;
The velocity of C is 9 / 10, 9 / 10 of that of B;
A's speed is 11 / 9 of C's, 11 / 9 of 9

What should be paid attention to in multiplication vertical calculation

Pay attention to carry and left shift method and decimal point. The left shift method means that the next multiplied data should be moved to the left one space below the previous data, and then add the decimal point after vertical addition