Johnny is buying planks of wood to build some tables. Each table needs a plank of wood for each of the legs and 5 planks of wood for the surface. If Johnny wants to build 5 tables, how many planks of wood does he need? Think carefully first, then make a decision:
Each table needs 1 plank of wood * 4 legs = 4 planks of wood for the legs. This means each table needs 4 planks of wood for legs + 5 planks of wood for the surface = 9 planks of wood. To build 5 tables, Johnny will therefore need 9 planks of wood * 5 tables = 45 planks of wood. So, the answer is 45.