1. 口算。
28 - 8 = 35 - 4 = 37 - 30 =
62 - 20 = 85 - 5 = 66 - 6 =
47 - 5 = 77 - 6 = 58 - 2 =
28 - 8 = 35 - 4 = 37 - 30 =
62 - 20 = 85 - 5 = 66 - 6 =
47 - 5 = 77 - 6 = 58 - 2 =
答案
$28 - 8 = 20$;$35 - 4 = 31$;$37 - 30 = 7$;$62 - 20 = 42$;$85 - 5 = 80$;$66 - 6 = 60$;$47 - 5 = 42$;$77 - 6 = 71$;$58 - 2 = 56$。
2. 直接写出得数。
44 - (9 - 6) = 55 - (8 - 4) = 64 + (3 + 7) =
35 - (15 + 5) = 70 + (10 + 10) = 50 - (15 - 5) =
44 + (33 - 3) = 57 - (55 - 5) = 49 + 1 + 20 =
44 - (9 - 6) = 55 - (8 - 4) = 64 + (3 + 7) =
35 - (15 + 5) = 70 + (10 + 10) = 50 - (15 - 5) =
44 + (33 - 3) = 57 - (55 - 5) = 49 + 1 + 20 =
答案
$44-(9 - 6)=41$;$55-(8 - 4)=51$;$64+(3 + 7)=74$;$35-(15 + 5)=15$;$70+(10 + 10)=90$;$50-(15 - 5)=40$;$44+(33 - 3)=74$;$57-(55 - 5)=7$;$49 + 1 + 20=70$。
3. 在$\bigcirc$里填上“>”“<”或“=”。
20 + 56$\bigcirc$86 51$\bigcirc$42 + 7 63 - 20$\bigcirc$36 - 20
34 + 6$\bigcirc$44 45$\bigcirc$63 - 20 20 + 13$\bigcirc$13 + 20
20 + 56$\bigcirc$86 51$\bigcirc$42 + 7 63 - 20$\bigcirc$36 - 20
34 + 6$\bigcirc$44 45$\bigcirc$63 - 20 20 + 13$\bigcirc$13 + 20
答案
$20 + 56\lt86$;$51\gt42 + 7$;$63 - 20\gt36 - 20$;$34 + 6\lt44$;$45\gt63 - 20$;$20 + 13=13 + 20$。
4. 在()里填上适当的数。
() + 8 = 78 () - 9 = 50 49 - () = 40
82 - () = 80 () + 40 = 42 () - 30 = 6
() + 8 = 78 () - 9 = 50 49 - () = 40
82 - () = 80 () + 40 = 42 () - 30 = 6
答案
70;59;9;2;2;36
5. 按得数从小到大排列。
25 + 20 100 - 70 37 + 4 30 - 3 55 + 6
() < () < () < () < ()
25 + 20 100 - 70 37 + 4 30 - 3 55 + 6
() < () < () < () < ()
答案
$(30 - 3) < (100 - 70) < (37 + 4) < (25 + 20) < (55 + 6)$
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