[CHOOHO]

Okay so it might seem like I just want an answer here but I really do love Chemistry and would love to know how to do this problem. Here's how it starts:
Muriatic acid is a solution of hydrochloric acid used by masons to clean brickwork and etch concrete. An experiment was carried out to determine the percent of hydrochloric acid in a bottle of muriatic acid by titration.

There's a part A to it which makes you find the M of NaOH which I already got (0.361). I am stuck on the rest though, look.
Part B) [Confirming answer only] A 50.00 mL sample of muriatic acid solution was diluted to a total volume of 1000.0 mL. Then 20.0 mL of the diluted acid required 27.40 mL of standard NaOH solution to reach the endpoint. Calculate the concentration of the diluted muriatic acid solution [I got 0.45 M for the HCL correct?]
c. Calculate the concentration of the original muriatic acid solution. [This I have no idea where to start]
d. The density of the original muriatic acid solution was found to be 1.15 g/mL. What is the percent by mass of HCl in the original
muriatic acid solution? [For this I am not sure what percent by mass of HCL means]
e. Laboratory grade hydrochloric acid is 37.0% HCl and has a density of 1.185 g/mL. Calculate the molarity of laboratory HCl. [I am pretty sure I can figure this one out]

[Borek]

http://www.chembuddy.com/?left=concentration&right=mass-percentage

http://www.chembuddy.com/?left=concentration&right=dilution-mixing

0.45M is wrong, but could be it is a typo.