Q8 of 33 Page 4

Verify a-(-b)= a + b for the following values of a and b:

(i) a = 21, b = 18


(ii) a = 118, b = 125


(iii) a = 75, b = 84


(iv) a = 28, b = 11

(i) We have given in the question that,


a = 21


b = 18


We have to prove that:


a – (-b) = a + b


Now,


a – (-b) = 21 – (-18)


= 21 + 18


= 39


Also,


a + b = 21 + 18


= 39


Therefore,


a – (-b) = a + b


Hence, verified


(ii) We have given in the question that,


a = 118


b = 125


We have to prove that:


a – (-b) = a + b


Now,


a – (-b) = 118 – (-125)


= 118 + 125


= 243


Also,


a + b = 118 + 125


= 243


Therefore,


a – (-b) = a + b


Hence, verified


(iii) We have given in the question that,


a = 75


b = 84


We have to prove that:


a – (-b) = a + b


Now,


a – (-b) = 75 – (-84)


= 75 + 84


= 159


Also,


a + b = 75 + 84


= 159


Therefore,


a – (-b) = a + b


Hence, verified


(iv) We have given in the question that,


a = 28


b = 11


We have to prove that:


a – (-b) = a + b


Now,


a – (-b) = 28 – (-11)


= 28 + 11


= 39


Also,


a + b = 28 + 11


= 39


Therefore,


a – (-b) = a + b


Hence, verified


More from this chapter

All 33 →
6

Rita goes 20 km towards east from a point A to the point B. From B, she moves 30 km towards west along the same road. If the distance towards east is represented by a positive integer, then how will you represent the distance travelled towards west? By which integer will you represent her final position from A?

 7

In a magic square each row, column and diagonal have the same sum. Check which of

the following is a magic square.


(i)



















5



-1



-4



-5



-2



7



0



3



-3



(ii)



















1



-10



0



-4



-3



-2



-6



4



-7


 9

Use the sign of >, < or = in the box to make the statements true:

(a) (-8) + (-4) ….. (-8) - (-4)


(b) (-3) + 7 – (19) ….. 15 – 8 + (-9)


(c) 23 – 41 + 11 ….. 23 – 41 – 11


(d) 39 + (-24) – (15) ….. 36 + (-52) – (-36)


(e) – 231 + 79 + 51 ….. – 399 + 159 + 81

 10

A water tank has steps inside it. A monkey is sitting on the topmost step (i.e, the first step). The water level is at the ninth step.


(i) He jumps 3 steps down and then jumps back 2 steps up. In how many jumps will he reach the water level?
(ii) After drinking water, he wants to go back. For this, he jumps 4 steps up and then jumps Back 2 steps down in every move. In how many jumps will he reach back the top step?
(iii) If the number of steps moved down is represented by negative integers and the number of steps moved up by positive integers, represent his moves in part (i)
and (ii) by completing the following: -3 + 2 -.....= -8 ; 4 -2 + 4 -2 .... = 8. In (a), the sum (-8) represents going down by eight steps. So, what will the sum 8 in (b) represent?