Madame Curie made some radium in her lab. She used 2/5 kg of the radium in an experiment and had 1 1/4 kg left . A. How much radium did she have at first?
B. If she performed the experiment twice, how much radium would she have left?​

This is what i found “an explicit formula designates the nth term of the sequence, as an expression of n (where n = the term's location). it defines the sequence as a formula in terms of n. this example is an arithmetic sequence(the same number, 5, is added to each term to get to the next term).” i hope this you for what your looking for. can you plz mark me brainliest?

The second and fourth answer are correct