In a large bowl, stir together the whole wheat flour, all-purpose flour and salt. Use a wooden spoon to stir in the olive oil and enough water to make a soft dough that is elastic but not sticky. Knead the dough on a lightly floured surface until it is smooth. Divide into 10 parts, or less if you want bigger breads. Roll each piece into a ball. Let rest for a few minutes.
Heat a skillet over medium heat until hot, and grease lightly. On a lightly floured surface, use a floured rolling pin to roll out the balls of dough until very thin like a tortilla. When the pan starts smoking, put a chapati on it. Cook until the underside has brown spots, about 30 seconds, then flip and cook on the other side. Continue with remaining dough.