Частина 2 — Вправи: 1162

1162. Спираючись на переставний і сполучний закони, виконайте додавання зручним способом:

1) –2 + (–3) + (–8) + (–7) = (–2 + (–8)) + (–3 + (–7)) = –10 + (–10) = –20;

2) 13 + 26 + (–3) + (–16) = (13 + (–3)) + (26 + (–16)) = 10 + 10 =

= 20;

3) –19 + 19,7 + (–91) = (–19 + (–91)) + 19,7 = –110 + 19,7 = –90,3;

4) 78,2 + (–105) + 11,8 = (78,2 + 11,8) + (–105) = 90 + (–105) = –15.

5) –13,6 + (–15,333) + (–6,4) + (–4,667) = (–13,6 + (–6,4)) + (–15,333 + (–4,667)) = –20 + (–20) = –40;

6) –71,4 + 31,8 + 25,2 + (–38,6) = (–71,4 + (–38,6)) + (31,8 + 25,2) = –110 + 57 = –53;

7) 25,3 + (–45,13) + (–20,3) + (–60,87) = (25,3 + (–20,3)) + (–45,13 + (–60,87)) = 5 + (–106) = –101.