Question

简便运算

9.75+99.75+999.75+9999.75+1.2

4.8+2.4*98

98+97-96-95+94+93-92-91+90+89-……-4-3+2+1

Answer 1

1. 9.75+99.75+999.75+9999.75+1.2
因为每个数都差0.25 而总共有4个 所以总共差4*0.25=1 所以原式=10+100+1000+10000+1.2-0.25*4
=1110.2
2. 因为4.8可以分为2*2.4 所以运用乘法结合律4.8+2.4*98
=2.4*2+2.4*98
=2.4*(2+98)
=2.4*100
=240
3.由题目得 相邻偶数相减为2 而相邻奇数相减也为2 所以原式为
98+97-96-95+94+93-92-91+90+89-……-4-3+2+1
=(98-96)+(97-95)+...+(6-4)+(5-3)+2+1
=24*2+2+1
=51

Answer 2

9.75+99.75+999.75+9999.75+1.2
=10-0.25+100-0.25+1000-0.25+10000-0.25+1.2
=11110-4*0.25+1.2
=11110.2

4.8+2.4*98
=2.4(2+98)
=2.4*100
=240

98+97-96-95+94+93-92-91+90+89-……-4-3+2+1
=(98+97-96-95)+(94+93-92-91)+90+89-……+(6+5-4-3)+2+1
=4+4+4……+4+2+1
=4*24+3
=99

98+97-96-95+94+93-92-91+90+89-……-4-3+2+1
=[(98+1)+(97+2)-(96+3)-(95+4)]+……+50+49
=99

Answer 3

9.75+99.75+999.75+9999.75+1.2
=10+100+1000+10000+1.2-0.25*4
=1110.2

4.8+2.4*98
=2.4*2+2.4*98
=2.4*(2+98)
=2.4*100
=240

98+97-96-95+94+93-92-91+90+89-……-4-3+2+1
=(98-96)+(97-95)+...+(6-4)+(5-3)+2+1
=24*2+2+1
=51

Answer 4

9.75+99.75+999.75+9999.75+1.2
=10+100+1000+10000+1.2-0.25*4
=10+100+1000+10000+1.2-1
=1110.2
4.8+2.4*98
=2.4*2+2.4*98
=2.4*(2+98)
=2.4*100
=240

98+97-96-95+94+93-92-91+90+89-……-4-3+2+1
=[(98+1)+(97+2)-(96+3)-(95+4)]+……+50+49
=99

Answer 5