0.279 ×355+0.645×279 Solve by equation

0.279 ×355+0.645×279 Solve by equation

0.279 ×355+0.645×279=279×0.355+0.645×279=279×（0.355+0.645）=279×1=279

A simple method is used to calculate. 355 + 260 + 140 + 245 & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; 987 - (287 + 135) 89 × 99 + 89 & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; 1050 △ 15 △ 7

（1）355+260+140+245，=（355+245）+（260+140），=600+400，=1000；（2）987-（287+135），=987-287-135，=700-135，=565；（3）89×99+89，=89×（99+1），=89×100，=8900；    （4）1050÷15÷7，=1050÷（15×7），=1050÷105，=10．

6.45 * 42 / 0.645 = simple method

Original formula = 42 * 6.45/0.645 = 42 * (6.45 / 0.645) = 42 * 10 = 420

A simple method of 35 times quarter + 0.25 times 48 + 17 times 25%

=(35+48+17)*0.25=25