Father 4× son now; 7× five years ago (Arvind): Arvind’s father is four times Arvind’s current age. Five years ago, the father was seven times Arvind’s age then. Find the father’s present age.

Introduction / Context:
Identical structure to a standard parent–child age system: one relation at present and one relation in the past. Solve linearly to get the present ages. The numeric values turn out the same as in similar problems because the coefficients match.

Given Data / Assumptions:

• Let Arvind be A and father be F (present).
• F = 4A.
• F − 5 = 7(A − 5).

Concept / Approach:
Substitute F = 4A into the second equation and solve for A, then compute F. The arithmetic mirrors earlier examples and is robust to sign errors if written stepwise.

Step-by-Step Solution:

Verification / Alternative check:
Five years ago: father 35, Arvind 5 (7×). Present: 40 vs 10 (4×). Both conditions hold.

Why Other Options Are Wrong:
35/70/84 are inconsistent with one or both relations.

Common Pitfalls:
Forgetting to subtract 5 from both ages for the past relation or misreading “four times” vs “seven times”.

Final Answer:
40 years