Madame Curie had
kg of radium at the beginning.
<h3>
Further Explanation</h3>
Madame Curie used ²/₅ kg for experiment
Radium left = 1¹/₄ kg
<u>Question:</u>
How much radium did she have at first?
The amount of radium that Madame Curie had at first :
= Radium for experiment+ the amount of radium left

we can do the additional if the denominator is the same, if not we need to find a common denominator, in this problem, the common denominator for 5 and 4 is 20, so the equation would be:
we change the mixed fraction into an improper fraction

So, at first, Madame Curie had 1
of radium
<h3>Learn more</h3>
Mixed fraction additional brainly.com/question/213168
Additional that have sum of 10 brainly.com/question/5146571
Mixed fraction brainly.com/question/745462
Keywords: mixed fraction, fraction, additional fraction, additional, common denominator, numerator