What would bethe heartof a personif thecardiac out putis 5l,blood volume in theventriclesat theend of diastole is 100ml and atthe end ofventricular systole is 50 ml.

Dear student,
The word "rate" is missing from the question. We have to calculate the heart rate of the person from the given data.
Volume of blood in ventricle at the end of diastole = 100 ml.
Volume of blood in ventricle at the end of systole = 50 ml.
Hence, stroke volume = (Volume of blood in ventricle at the end of diastole - Volume of blood in ventricle at the end of systole) = (100-50) = 50 ml.
Now, cardiac output = 5 l = 5000 ml.
Again we know, heart rate = $\frac{\mathrm{Cardiac} \mathrm{output}}{\mathrm{Stroke} \mathrm{volume}}$ 
Hence, heart rate of the person = $\frac{5000}{50}$= 100

Regards