РОЗДІЛ 3. РАЦІОНАЛЬНІ ЧИСЛА ТА ДІЇ З НИМИ - § 33. Властивості додавання

1110. Виконай дії:

1) 15/6 + (-24/9) + (-5/8) + 27/12 =
= 15/6 + 27/12 + ((-24/9) + (-5/8)) =
= 310 + 7/12 + (-232 + 45/72) =
= 317/12 + (-277/72) = 45/12 + (-35/72) =
= 130 - 5/72 = 125/72;

2) -74/9 + 63/4 + (-25/12) =
= -74/9 + (-25/12) + 63/4 = -916 + 15/36 + 63/4 =
= -931/36 + 63/4 = -(931/36 - 63/4) =
= -331 - 27/36 = -34/36 = -31/9;

3) -21/5 + 921/25 + (-57/10) =
= -21/5 + (-57/10) + 921/25 =
= -72 + 7/10 + 921/25 = -79/10 + 921/25 =
= 921/25 - 79/10 = 846/25 - 79/10 =
= 1184 - 90/100 = 194/100 = 147/50;

4) -42,08 + (-62/5) + (-73/4) = 

= -(42,08 + 6,4 + 7,75) = -56,23;

5) -5,1 + (-33/10) + 51/3 + (-0,7) = 
= -5,1 + (-3,3) + (-0,7) + 51/3 = -9,1 + 51/3 = 
= -(91/10 - 51/3) = -(811/10 - 51/3) = 
= -333 - 10/30 = -323/30;

6) -32/5 + (-8,75) + 153/10 + (-68/15) =
= -32/5 + (-83/4) + (-68/15) + 153/10 =
= -1724 + 45 + 32/60 + 153/10 =
= -17101/60 + 153/10 = -1841/60 + 153/10 =
= -(1841/60 - 153/10) = -341 - 18/60 = -323/60.