3. As shown in Figure 6, square
$E F G H$ is inscribed in $\triangle A B C$.
Let $B C=\overline{a b}$ (this is a
two-digit number), $E F=c$,
the height of the triangle $A D=d$.
It is known that $a, b, c, d$ are exactly
four consecutive positive integers in ascending order. Find the area of $\triangle A B C$.
(1997, Anhui Province Junior High School Mathematics Competition)
(Given: $b=a+1, c=\frac{\overline{a b} \times d}{\overline{a b}+d}=$ $\frac{(10 a+a+1)(a+3)}{10 a+a+1+a+3}=a+2$, we get $a=1$ or $a=$ 5. Therefore, $S_{\triangle A B C}=24$ or 224.)