Learn Arabic (Modern Standard): هل مشيت خطوة واحدة؟

The suffix ـت at the end of مشيت shows it is the past tense for 'you'. In written Arabic without vowel marks, this exact spelling can be read as 'mashayta' (you, masculine) or 'mashayti' (you, feminine).

Why does the number 'one' (واحدة) come after the noun (خطوة)?

In Arabic, the numbers one and two behave like adjectives. Instead of saying 'one step', you literally say 'step one' (خطوة واحدة), just as you would place any other adjective after the noun it describes.

Why use واحدة instead of the masculine form واحد?

The word for step, خطوة, is a feminine noun (you can tell by the ة at the end). Because the number one acts as an adjective, it must match the gender of the noun it counts.

How would I change this sentence to ask 'How many steps did you walk?' using كم?

You would replace the yes/no question word هل with كم (how many) and drop the number 'one'. You would say كم خطوة مشيت؟ (How many steps did you walk?). Notice that after كم, we always use the singular form of the noun, just like we do here with خطوة.