Calculation of 9.8 * 4.5 2.4 * 2.5 * 3.7 12.5 * 9.8-4.9 * 5 with a simple method

Calculation of 9.8 * 4.5 2.4 * 2.5 * 3.7 12.5 * 9.8-4.9 * 5 with a simple method

1、 9.8 * 4.5 = (10-0.2) * 4.5 = 45-0.9 = 44.1
2、 2.4 * 2.5 * 3.7 = 0.4 * 6 * 0.5 * 5 * 3.7 = (0.4 * 0.5) * (6 * 5) * 3.7 = 0.2 * 30 * 3.7 = 6 * 3.7 = 22.2
3、 12.5 * 9.8-4.9 * 5 = 4.9 * (12.5 * 2-5) = 4.9 * 20 = 98
Hope to help you.

There is a fraction, the numerator plus 5 can be reduced to 2 / 3, and the numerator minus 5 can be reduced to 7 / 18. What is the number?

(2 / 3 + 7 / 18) △ 2 = 19 / 36, so this number is 19 / 36

If there is a fraction, the addition of 5 to the numerator can be reduced to 2 / 3, and the subtraction of 5 from the numerator can be reduced to 7 / 18

2/3=12/18
(12-7)=5
5÷（5+5）=(1/2)
The unit of this fraction is (1 / 18) × (1 / 2) = 1 / 36
The score is: 2 / 3-5 / 36 = 19 / 36
Or 7 / 18 + 5 / 36 = 19 / 36

18 of 13 × 5.16 + 6.16% + 18 of 5 (simple calculation)

There is no easy way
=2322/325+77/1250+18/5
=13101 / 10 and 16250