MCQ
Choose the correct answer from the given four options: If the common difference of an $AP$ is $5,$ then what is $a_{18}-a_{13} ?$
- A$5$
- B$20$
- ✓$25$
- D$30$
✓
Answer
Correct option: C.
$25$
Given, the common difference of $AP$ i.e., $d=5$
${\left[\therefore a_n=a+(n-1) d\right]}$
$\text {Now, } a_{18}-a_{13}=a+(18-1) d-[a+(13-1) d]$
$a_{18}-a_{13}=a+17 \times 5-a_{12} \times 5$
$a_{18}-a_{13}=85-60$
$a_{18}-a_{13}=25$
${\left[\therefore a_n=a+(n-1) d\right]}$
$\text {Now, } a_{18}-a_{13}=a+(18-1) d-[a+(13-1) d]$
$a_{18}-a_{13}=a+17 \times 5-a_{12} \times 5$
$a_{18}-a_{13}=85-60$
$a_{18}-a_{13}=25$
Need a full question paper?
Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.
Explore more
Similar questions
A kite is flying at a height of $45 m$ above the ground. The string attached to the kite is temporarily tied to a point on the ground. The inclination of the string with the ground is $60^{\circ}$. Find the length of the string assuming that there is no slack in the string. $($Use $\sqrt{3}=1.732$ )
→Which of the following is not a measure of central tendency ?
The circumference of a circle is equal to the sum of the circumferences of two circles having diameters $34 \ cm$ and $10 \ cm$. The radius of the new circle is
→Given that $2x + 3y = 11, 2x - 4y = -24$ and $y = m, x + 3,$ then the value of $m$ is :
→The vertices of a triangle $OAB$ are $O (0,0), A (4,0)$ and $B (0,6)$. The median $AD$ is drawn on $OB$ . The length $A D$ is
→In Fig. graphs of two linear equations are shown. The pair of these linear equations is
In a $\triangle\text{ABC},$ AD is the bisector of $\angle\text{BAC}.$ If AB = 8cm, BD = 6cm and DC = 3cm. Find AC:
→If the equation $x^2+ 6(k + 2)x + 9k = 0$ has equal roots then $k = ?$
→The probability of getting a bad apple in a box of 400 apples is 0.035. The total number of bad apples is
From a light house the angles of depression of two ships on opposite sides of the light house are observed to be $30^\circ$ and $45^\circ$ . If the height of the light house is $h$ metres, the distance between the ships is :
→