Выполните сложение, выбирая удобный порядок вычислений:
1) (42 + 37) + 58;
2) 29 + (98 + 71);
3) (215 + 818) + 785;
4) 634 + (458 + 166);
5) 183 + 732 + 268 + 317;
6) 339 + 584 + 416 + 661;
7) (15083 + 1458) + (4917 + 6542);
8) (1654 + 18135) + (7346 + 11865).
(42 + 37) + 58 = (42 + 58) + 37 = 100 + 37 = 137
29 + (98 + 71) = (29 + 71) + 98 = 100 + 98 = 198
(215 + 818) + 785 = (215 + 785) + 818 = 1000 + 818 = 1818
634 + (458 + 166) = (634 + 166) = 800 + 458 = 1258
183 + 732 + 268 + 317 = (183 + 317) + (732 + 268) = 500 + 1000 = 1500
339 + 584 + 416 + 661 = (339 + 661) + (584 + 416) = 1000 + 1000 = 2000
(15083 + 1458) + (4917 + 6542) = (15083 + 4917) + (1458 + 6542) = 20000 + 8000 = 28000
(1654 + 18135) + (7346 + 11865) = (1654 + 7346) + (18135 + 11865) = 9000 + 30000 = 39000