Question

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. how much radium did she have at first?

Answer 1

SHE HAD 3/5 TO START I BELIEVE

Answer 2

Madame Curie had $1\frac{13}{20}$ kg of radium at the beginning.

Further Explanation

Madame Curie used ²/₅ kg for experiment

Radium left = 1¹/₄ kg

Question:

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

$\boxed {= \frac{2}{5} + 1\frac{1}{4} }$

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

$\boxed {=\frac{2}{5} + 1\frac{1}{4} } \\\boxed {=\frac{2}{5} + \frac{5}{4} =( \frac{2 \times4}{5 \times4}) + (\frac{5 \times5}{4 \times5}) } \\\boxed {= \frac{8+25}{20} =\frac{33}{20} = 1\frac{13}{20} }$

So, at first, Madame Curie had 1$1\frac{13}{20}$ of radium

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Keywords: mixed fraction, fraction, additional fraction, additional, common denominator, numerator