Class 10 Maths Arithmetic Progression (AP) – Which Term Is 78? | Video & Image Solution
Arithmetic Progression (AP) is an important chapter in Class 10 Maths and frequently asked in board exams. In this post, we solve the question: Find the number of terms in each of the following APs:18, 15½,13 ......., 47? using a clear, step-by-step method based on NCERT concepts. This problem helps students understand the formula of the nth term of an AP and how to apply it correctly in exam-oriented questions.
To make learning easier and more effective, this post includes a complete video solution explaining each step in a simple way, along with a well-labeled image solution for quick revision. These resources are ideal for CBSE,PSEB,UPBOARD,BIHARBOARD,HARYANABOARD,MPBOARD,ALLSTATEBOARD Class 10 students preparing for board exams, school tests, and competitive exams.
Question:- Find the number of terms in each of the following APs:18, 15½,13 ......., 47.
🎥 Watch Detailed Video Solution:
Find the number of terms in each of the following APs:18, 15½,13 ......., 47.
solutions:-
Step 1: Identify the values
First term (a) = 18
Second term = 15½ = 15.5
Common difference (d) = 15.5 − 18
d = -2.5
Last term (l) = -47
Step 2: Use nth term formula
an = a + (n-1)d
-47 = 18 + (n-1)(-2.5)
Step 3: Solve the equation
-47 = 18 - 2.5(n-1)
-47-18 = - 2.5(n-1)
-65 = - 2.5(n-1)
-65/-2.5 = n-1
26 = n-1
n= 26 + 1
n = 27
Final Answer = 27
The given AP has 27 terms.
