1. คิดเร็ วทัวไป
่
10x10 = 10010= 10025= 10x0.10 = 1000.10= 1002.5=
20x5= 10050= 1002= 20x0.5= 1000.50= 1000.02=
50x2= 1004= 1005= 50x0.2= 1000.4= 1000.05=
25x4= 10020= 1000250= 25x0.4= 1000.20= 10000.250=
40x25= 40x2.5=
1000100= 4008= 10000.100= 1000.02=
100x10= 100x0.01=
100040= 20050= 10000.40= 1000.005=
25x8= 2.5x8=
10008= 50025= 10000.8= 1000.01=
80x25= 80x2.5=
100025 75025= 10000.25 1000.50=
50x20= 50x0.20=
1. 25.49 + 3 4 – 2.78 = …………. 10. (2 5  3 4 )  7 ) = ………..
5 6 35 20
11. ( 25.50 x 8 ) + ( 256.3 ) = …………..
1.25 3.05 0.04 100
2.   =………… 2 3
100 1000 10 12. 4 =……………………
3 5
7 3
3 4 15 2
(  ) 8 30
3 4 3 4
3. 5 9 20 = …………………. 13. ( 6 +7 ) – ( 5 + 3 ) = ………
4 16
 14. ( 35.58 x 1.2 ) – ( 115.63 – 96 ) = ……….
7 21
15. ( 85 x 96 ) + ( 2,079  99 ) = ……….
4. 1

2

3
=…………… 16. 3.45 + 385 – 1.896 = ………………..
10 100 1000 1000
17. ( 0.05 x 1.2 ) + 2 17 =…………………
4 6 2 25
5. 3 7 8 =……………….
5 7 3 18. ( 1876.34 x 4.7 ) – ( 5.06 x 1.3 ) = …………
19. ( 83 + 94 ) – ( 3,038  49 ) = ……………
7 3
 20. 56  244  7 = ……………..
6. 25 72 = …………… 100 1000 20
14 6

50 9
2491 3

21. 53 47 = ………………….
3.25 3
7.  4.098  3 = ……… 6
1000 4 22. ( 48.56 x 38 ) + ( 9.001 – 8 ) = ……………
23. ( 55  24 )  2 3 = ……………….
0.048
8. (0.12 x 0.05) + =…….. 150 400 40
100
1.25 1.2 0.08 24. ( 6,500 – 258 ) x ( 3,008  94 ) x ( 658 x 0 ) =……..
9.   = …………
25 0.6 4 25. (0.12)2 + (0.04)2 – ( 0.09)2 = ……………….