How many planks of size 2 m × 25 cm × 8 cm can be prepared from a wooden block 5 m long,

Total volume of the block $=(500 \times 70 \times 32)=1120000 \mathrm{~cm}^{3}$

Total volume of each plank $=200 \times 25 \times 8=40000 \mathrm{~cm}^{3}=200 \times 25 \times 8=40000 \mathrm{~cm}^{3}$

$\therefore$ Total number of planks that can be made $=\frac{\text { Total volume of the block }}{\text { Volume of each plank }}=\frac{1120000}{40000}=28$ planks