100道趣味题参考答案和提示(4)
(5)原式=2×(1+3+5+…+99)=5100
(6)原式=4×(1+3+5+…+99)=10200
(7)原式=0.1×(1+3+5+…+99)=255.
2 (1)原式=(2+22+23+…+2100)-(2+22+23+…+249)=2101-249
4 (1)2100
(2)2+22+23+…+2100=2101-2
29.1 (略)2(略)3>
4 (1)20(2)180(3)80(4)120
30.1 (略)
2 (1)原式=(456-123)+789=1122
(2)原式=123+789-456=456
3 (1)25(2)20
31.1 (略)
2 (1)200(2)50(3)900
(4)4(5)100(6)200
32.1 (略) 2(略)
3 ①和④,②和③,⑤和⑥
33.1(略)
3 (1)a-b1-b2-b3-…-bn
(2)a-b1+b2+b3+…+bn
34.1 (略)
2 (1)a÷b1÷b2÷…÷bn
(2)a÷b1×b2×b3×…×bn
3 (略)
35.1 (1)原式=250÷25+2.5÷25=10.1
(2)原式=(90+8)÷98=1
(3)原式=7878÷78+78÷78=102
(4)原式=(1.3+3.5)÷4.8=1
(5)原式=(789-333)÷456=1
(6)原式=3636÷36-36÷36=100
2 相等
3 (1)原式=(1+11+111+1111+11111)÷12345=1