Answer: $308.

Solution:

Let T and F be the initial numbers of $2 and $5 notes. We have

(1) T + F = 148.

After buying the bag, the number of $5 notes she has is 0.4 F.

After her receiving another six $2 notes, the number of $5 notes she has is T + 6.

We are told that she then has thrice as many $2 notes as $5 notes.

Thus,

(2) 3 × 0.4 F = T + 6.

From (1), we have T = 148 – F. Plug this into (2) to get

3 × 0.4 F = 148 – F + 6.

Rearranging, we have 2.2 F = 154, and thus F = 70.

So T = 78.

And so the money she has at the end of the day is

0.4 F × 5 + (T + 6) × 2 = 0.4 × 70 × 5 + (78 + 6) × 2 = 140 + 168 = $308.

Hope this helps and feel free to ask for any clarifications.

– Dr. Choo Yan Min

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