El arquitecto pidió una medida aproximada primero y el número exacto después.

Because pedir is a stem-changing verb. In the preterite, the e changes to i in the third-person forms:

• yo pedí
• tú pediste
• él/ella/usted pidió
• nosotros pedimos
• vosotros pedisteis
• ellos/ellas/ustedes pidieron

So El arquitecto pidió... means The architect asked for / requested...

Pedir and preguntar are not the same.

• pedir = to ask for, to request
• preguntar = to ask a question

In this sentence, the architect is requesting information, so pidió is the natural choice.

• pidió una medida aproximada = asked for an approximate measurement
• preguntó una medida aproximada would sound wrong

A useful pattern is:

• preguntar algo = ask something
• preguntar por algo = ask about something
• pedir algo = ask for something

Because the nouns are different genders:

• medida is feminine → una medida aproximada
• número is masculine → el número exacto

In Spanish, articles and adjectives usually agree with the noun in gender and number.

So:

• una
  • medida
    • aproximada
• el
  • número
    • exacto

In Spanish, descriptive adjectives often come after the noun.

So:

• an approximate measurement → una medida aproximada
• the exact number → el número exacto

Putting the adjective before the noun is sometimes possible in Spanish, but it often changes the tone, emphasis, or sounds less natural. In this sentence, the standard order is noun + adjective.

Here, medida means measurement or dimension.

Depending on context, medida can mean different things:

• measurement
• size
• dimension
• measure (in some technical or abstract contexts)

In this sentence, una medida aproximada suggests that the architect first wanted a rough measurement, not the precise final figure yet.

Because aproximada describes medida, and medida is feminine singular.

Agreement works like this:

• medida → feminine singular
• adjective must match → aproximada

Compare:

• una medida aproximada
• un cálculo aproximado
• unas medidas aproximadas

Because exacto is an adjective, and it describes the noun número.

• el número exacto = the exact number

By contrast, exactamente is an adverb, and it would modify a verb, adjective, or whole statement.

Compare:

• el número exacto = the exact number
• No lo sé exactamente = I don’t know it exactly

So in this sentence, an adjective is needed, not an adverb.

They show the order of events.

• primero = first
• después = afterwards / later

So the sentence says the architect wanted one thing first and another thing later.

They function here as adverbs:

• pidió una medida aproximada primero
• y el número exacto después

Spanish often places these time/order words flexibly, and this sentence is perfectly natural.

Yes. Spanish word order is often more flexible than English, as long as the meaning stays clear.

For example, these are also natural:

• El arquitecto pidió primero una medida aproximada y después el número exacto.
• Primero, el arquitecto pidió una medida aproximada y después el número exacto.

The original sentence is fine, but many learners may be more used to seeing primero and después placed before the parts they modify.

Because these are direct objects that are things, not people.

Spanish uses the personal a mainly before specific human direct objects.

Compare:

• Pidió una medida aproximada. → no a, because it is a thing
• Vio al arquitecto. → a is used, because it is a person

So in this sentence, no a is needed.

Spanish often leaves out repeated words when they are understood from context.

The full version would be:

• El arquitecto pidió una medida aproximada primero y pidió el número exacto después.

But repeating pidió is unnecessary, so Spanish naturally omits it:

• El arquitecto pidió una medida aproximada primero y el número exacto después.

This is similar to English:

• He asked for an approximate measurement first and the exact number later.

We do not need to repeat asked for in English either.

Pidió is the preterite tense of pedir.

The preterite is used for a completed action in the past. Here, the sentence refers to a finished sequence:

1. the architect asked for an approximate measurement
2. later, he asked for the exact number

So the preterite fits well because the actions are presented as completed past events.

Yes, depending on context. Spanish could also use expressions like:

• la cifra exacta
• la medida exacta
• el dato exacto

But el número exacto is clear and natural if the speaker is focusing on the precise numerical value.

The best choice depends on what exactly is being measured:

• length?
• quantity?
• dimensions?
• cost?
• total count?

So the sentence is grammatically fine; another noun might simply be more specific in a different context.