Grade 4 Volume 2 vertical calculation 200

Grade 4 Volume 2 vertical calculation 200

The first question on page 33 of mathematics fifth grade of summer homework of Jiangsu Education Press in 2013
Known: 2 / 1 = 1-2 / 1
6 / 1 = 2 times 3 / 1 = 2 / 1-3 / 1
12 / 1 = 3 times 4 / 1 = 3 / 1-4 / 1
According to the above formula, the reaction law is calculated as follows:
2/1+6/1+12/1+20/1+30/1+42/1+56/1+72/1+90/1
(Note: / denotes a fractional line, read from left to right, e.g. 2 / 1 read as half)

1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9+1/9-1/10=1(-1/2+1/2)(-1/3+1/3)(-1/4+1/4)(-1/5+1/5)(-1/6+1/6)(-1/7+1/7)(-1/8+1/8)(-1/9+1/9)-1/10=1-1/10=9/10

31 gas stations, 34 training rooms 1, 38 gas stations 2, 40 gas stations and 46 gas stations will not,

9 of 16 + 3 of 8 = 1534 of 16.1 large: 1989 of 1990 small: 1838.2 of 19 (456-399) divided by (80-77) = 19 m 80 times 19-456 = 1064 m 40 8-1 = 7 384 divided by 8 = 48 square cm 48 times 7 = 336 square cm 46