1. We decided to go abroad.

2. We made up our mind to go abroad.
3. We made a decision to go abroad.
4. We made up our minds to go abroad.

(Are they all interchangable? Do we have to use the plural form 'minds' or the singular form 'mind'?)

5. We determinded to go abroad.
6. We made a determination to go abroad.
7. We made up our determination to go abroad.

(Are the three sentences the same?)

1. We decided to go abroad.

2. We made up our mind to go abroad.
These above would just use the word the plural form of mind.
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and yes all three last sentences are the same.

1. "We decided to go abroad." This sentence is in the past tense and conveys the idea that a choice was made to go abroad. It is a simple and clear statement.

2. "We made up our mind to go abroad." This sentence, similar to the first, indicates a decision was made but adds the phrase "made up our mind," which means to reach a final decision or reach a conclusion. However, it uses the singular form "mind" instead of the plural form "minds."

3. "We made a decision to go abroad." This sentence also expresses the idea that a choice was made to go abroad. However, it uses the singular form "decision" instead of the plural form "minds."

4. "We made up our minds to go abroad." This sentence, like the second one, reinforces the idea of a final decision being made using the phrase "made up our minds." It uses the plural form "minds" to indicate that multiple individuals reached the conclusion to go abroad.

In summary, sentences 1, 2, 3, and 4 are similar in meaning but some vary in terms of singular or plural usage. The choice between using the singular or plural form depends on whether you are referring to a collective decision made by multiple people (using the plural form like in sentence 4) or an individual decision (using the singular form like in sentences 2 and 3).

Regarding sentences 5, 6, and 7:

5. "We determined to go abroad." This sentence indicates a strong resolve or a firm decision to go abroad, using the verb "determined."

6. "We made a determination to go abroad." This sentence conveys a similar meaning to the previous one, expressing a strong resolve or decision to go abroad. It uses the noun form "determination" instead of the verb form "determined."

7. "We made up our determination to go abroad." This sentence combines the idea of reaching a conclusion or making a decision with the noun form "determination." However, the phrase "made up our determination" is less commonly used than the previous options and might not be as clear in terms of conveying the intended meaning.

In summary, sentences 5, 6, and 7 convey a similar meaning, but sentence 7 may be less commonly used and may not be as clear in terms of expressing the intended message.