question_answer 16)

Find (a) \[35(20)\] (b) \[72-(90)\] (c) \[(15)(18)\] (d)\[(20)(13)\] (e) \[23(12)\] (j) \[(32)(40)\] TIPS To subtract an integer from another integer, we add additive inverse of the integer that is being subtracted to the other integer.

Answer:

(a) We have, \[35(20)=35+\](Additive inverse of 20) \[=35+(20)\] \[=15+20+(-20)\] \[[\because 35=20+15]\] \[=15+0=15\] \[[\because 20+(-20)=0]\] (b) We have, \[7290=72+\](Additive inverse of 90) \[=72+(-90)=72+(-72)+(-18)\] \[[\because 90=72+18\Rightarrow -90=-72+(-18)]\] \[=0+(-18)=-18\] \[[\because 72+(-72)=0]\] (c) We have, \[(15)(-18)=15+\](Additive inverse of ?18) \[=-15+18\] \[=(-15)+(15)+(3)\] \[[\because 18=15+3]\] \[=0+3=3\] \[[\because (-15)+(15)=0]\] (d) We have, \[(-20)(13)=(-20)+\](Additive inverse of 13) \[=(20)+(-13)=(20+13)=33\] (e) We have, \[23(-13)=23+\](Additive inverse of ?12) \[=23+12=35\] (f) We have, \[(32)(40)=(32)+\](Additive inverse of ?40) \[=(-32)+40=(-32)+(32)+(8)[\because 40=32+8]\] \[=0+8=8\] \[[\because (-32)+(32)=0]\]