The sweets were distributed in the ratio 3:5:7, where John received the smallest share. According to the problem, John received 25 sweets. This 25 represents John's portion, corresponding to the smallest ratio (which is 3).

Let's denote the total number of sweets by $T$, and let’s assign variables to the parts of the ratio:

• John's share = 3 parts
• Second pupil's share = 5 parts
• Third pupil's share = 7 parts

The total number of parts is $3 + 5 + 7 = 15$.

Since John's share (3 parts) corresponds to 25 sweets, we can set up a proportion to find the value of one part:

$\frac{25}{3} = \text{one part}$

Thus, each part is:

$\frac{25}{3} \approx 8.33 \text{ sweets per part}.$

Now, to find the total number of sweets $T$, we multiply the total number of parts by the number of sweets per part:

$T = 15 \times 8.33 \approx 125 \text{ sweets}.$

Therefore, the teacher originally had 125 sweets.

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Do you want more details or have any questions?

Here are some related questions:

1. How many sweets did the second pupil receive?
2. How many sweets did the third pupil receive?
3. If John received 30 sweets instead of 25, how many sweets would there have been in total?
4. What is the ratio of the number of sweets between the second and third pupils?
5. If the teacher added more pupils, how would the ratio change?

Tip: When dealing with ratios, always break the problem down by first identifying the "parts" and then scaling them to match the known quantity.