MCQ
Using suitable identity, evaluate $(7.5)^2$
- ✓$56.25$
- B$56.5$
- C$56.025$
- D$81$
✓
Answer
Correct option: A.
$56.25$
A. $56.25$
Solution:
Writing $7.5 = 7 + 0.5$
$(7.5)^2 = (7 + 0.5)^2$
Using $(a + b)^2 = a^2 + b^2 + 2ab,$ we have $(7.5)^2 = (7 + 0.5)^2 = 7^2 + 2 × 7 \times 0.5 + (0.5)^2= 49 + 7 + 0.25 = 56.25$
Solution:
Writing $7.5 = 7 + 0.5$
$(7.5)^2 = (7 + 0.5)^2$
Using $(a + b)^2 = a^2 + b^2 + 2ab,$ we have $(7.5)^2 = (7 + 0.5)^2 = 7^2 + 2 × 7 \times 0.5 + (0.5)^2= 49 + 7 + 0.25 = 56.25$
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