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Arithmetic Progressions
NCERT Exemplar
CBSE
Grade 10
Question:
Determine the $10^{\text{th}}$ term from the end of the AP: $4, 9, 14, \dots, 254$.
Step-by-Step Solution
Key Concept: $n^{\text{th}}$ term from the end $= l - (n-1)d$.
Here last term $l = 254$, first term $a = 4$, common difference $d = 9 - 4 = 5$. [0.5 Mark] $10^{\text{th}}$ term from the end $= l - (10 - 1)d = 254 - 9(5) = 254 - 45 = 209$. [1.5 Marks]
--- 🎯 Official CBSE Marking Scheme: Identifying $l = 254$ and $d = 5$: 0.5 Mark Applying formula $l - 9d$ and calculating 209: 1.5 Marks
Correct Answer:
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