1440 tons of grain were brought to a silo over two days. on the second day, 80% of the amount of the grain delivered during the first day was brought in. how many tons of grain were delivered to the silo on the first day?

Ascientist wants to use a model to present the results of his detailed scientific investigation. why would a model be useful? a )because the model makes the concepts easier to understand b) because the model is easy to put together and to use c) because the model prevents other scientists from asking questions d) because the model requires the audience to pay full attention to it i don't know what to choose because between a and d a is much more likely than d because it only wants to get the attention of the audience. i'm confuse.