1
Question
Find the value of 1 - 2 + 3 - 4 + 5 - 6 +........... + 19 - 20.
Open in App
Solution
Here,
(1−2)=−(2−1)=−1
(3−4)=−(4−3)=−1
.
.
(19−20)=−(20−19)=−1.
[1 mark]
There are 10 pairs having a value -1.
∴1−2+3−4+5−6 +...........+19−20
= +10×(−1)= −10 [∵x×(−y)=−xy]
[1 mark]
Here,
(1−2)=−(2−1)=−1
(3−4)=−(4−3)=−1
.
.
(19−20)=−(20−19)=−1.
[1 mark]
There are 10 pairs having a value -1.
∴1−2+3−4+5−6 +...........+19−20
= +10×(−1)= −10 [∵x×(−y)=−xy]
[1 mark]
Suggest Corrections
3
Similar questions
View More
Join BYJU'S Learning Program
Explore more
Join BYJU'S Learning Program
