Question.
In the following APs, find the missing terms in the boxes :
(i) $2, \square, 26$
(ii) $\square, 13, \square, 3$
(iii) $5, \square, \square, 9 \frac{1}{2}$
(iv) $-4, \square, \square, \square, \square, 6$
(v) $\square, 38, \square, \square, \square,-22$
In the following APs, find the missing terms in the boxes :
(i) $2, \square, 26$
(ii) $\square, 13, \square, 3$
(iii) $5, \square, \square, 9 \frac{1}{2}$
(iv) $-4, \square, \square, \square, \square, 6$
(v) $\square, 38, \square, \square, \square,-22$
Solution:
(i) $\mathrm{a}=2, \mathrm{a}+2 \mathrm{~d}=26 \quad \Rightarrow 2+2 \mathrm{~d}=26$
$\Rightarrow 2 \mathrm{~d}=26-2=24 \quad \Rightarrow \mathrm{d}=12$
Then the missing term
$t_{2}=a+d=2+12=14$
(ii) $a+d=13$ ...(1)
$a+3 d=3$ ...(2)
Subtracting (1) from (2), we get
$(a+3 d)-(a+d)=3-13$
$\Rightarrow 2 \mathrm{~d}=-10 \Rightarrow \mathrm{d}=-5$
from $(1), a-5=13$
$\Rightarrow a=18$
Therefore, the first missing term is 18
The next missing term
$t_{3}=t_{2}+d=13+(-5)=8$
(iii) $a=5$
$a_{4}=9 \frac{1}{2}=\frac{19}{2} \quad a+3 d=\frac{19}{2}$
$\frac{19}{2}=5+3 d$
$\frac{19}{2}-5=3 d$
$\frac{9}{2}=3 d$
$d=\frac{3}{2}$
$a_{2}=a+d=5+\frac{3}{2}=\frac{13}{2}$
$a_{3}=a+2 d=5+2\left(\frac{3}{2}\right)=8$
Therefore, the missing terms are $\frac{13}{2}$ and 8 respectively.
(iv) $a=-4$
$a_{6}=6$
$a+5 d=6$
$6=-4+5 \mathrm{~d}$
$10=5 \mathrm{~d}$
$\mathrm{d}=2$
$a_{2}=a+d=-4+2=-2$
$a_{3}=a+2 d=-4+2(2)=0$
$a_{4}=a+3 d=-4+3(2)=2$
Therefore, the missing terms are $-2,0,2$, and 4 respectively.
(v) $\mathrm{a}_{2}=38$
$a_{6}=-22$
$38=a+d$ ...(1)
$-22=a+5 d$ ...(2)
On subtracting equation (1) from (2), we obtain
$-22-38=4 d$
-60=4 d
$\mathrm{d}=-15$
$a=a_{2}-d=38-(-15)=53$
$a_{2}=a+2 d=53+2(-15)=23$
$a_{4}=a+3 d=53+3(-15)=8$
$a_{5}=a+4 d=53+4(-15)=-7$
Therefore, the missing terms are $53,23,8$, and $-7$ respectively.
(i) $\mathrm{a}=2, \mathrm{a}+2 \mathrm{~d}=26 \quad \Rightarrow 2+2 \mathrm{~d}=26$
$\Rightarrow 2 \mathrm{~d}=26-2=24 \quad \Rightarrow \mathrm{d}=12$
Then the missing term
$t_{2}=a+d=2+12=14$
(ii) $a+d=13$ ...(1)
$a+3 d=3$ ...(2)
Subtracting (1) from (2), we get
$(a+3 d)-(a+d)=3-13$
$\Rightarrow 2 \mathrm{~d}=-10 \Rightarrow \mathrm{d}=-5$
from $(1), a-5=13$
$\Rightarrow a=18$
Therefore, the first missing term is 18
The next missing term
$t_{3}=t_{2}+d=13+(-5)=8$
(iii) $a=5$
$a_{4}=9 \frac{1}{2}=\frac{19}{2} \quad a+3 d=\frac{19}{2}$
$\frac{19}{2}=5+3 d$
$\frac{19}{2}-5=3 d$
$\frac{9}{2}=3 d$
$d=\frac{3}{2}$
$a_{2}=a+d=5+\frac{3}{2}=\frac{13}{2}$
$a_{3}=a+2 d=5+2\left(\frac{3}{2}\right)=8$
Therefore, the missing terms are $\frac{13}{2}$ and 8 respectively.
(iv) $a=-4$
$a_{6}=6$
$a+5 d=6$
$6=-4+5 \mathrm{~d}$
$10=5 \mathrm{~d}$
$\mathrm{d}=2$
$a_{2}=a+d=-4+2=-2$
$a_{3}=a+2 d=-4+2(2)=0$
$a_{4}=a+3 d=-4+3(2)=2$
Therefore, the missing terms are $-2,0,2$, and 4 respectively.
(v) $\mathrm{a}_{2}=38$
$a_{6}=-22$
$38=a+d$ ...(1)
$-22=a+5 d$ ...(2)
On subtracting equation (1) from (2), we obtain
$-22-38=4 d$
-60=4 d
$\mathrm{d}=-15$
$a=a_{2}-d=38-(-15)=53$
$a_{2}=a+2 d=53+2(-15)=23$
$a_{4}=a+3 d=53+3(-15)=8$
$a_{5}=a+4 d=53+4(-15)=-7$
Therefore, the missing terms are $53,23,8$, and $-7$ respectively.