What is the ratio of the total number of 6B-Pencils sold by stores C and D…

Concept: When a table supplies one quantity together with the ratio that links it to a second quantity, the second quantity is recovered by scaling — if the ratio of the first to the second is a : b, then second = first × (b / a). A ratio between two derived totals is then built by adding the recovered values and reducing that pair to its lowest terms.

Application — recover each store's 6B-Pencil count from its own table row:

1. Store A: HB-Pencils sold = 216 with HB : 6B = 9 : 5, so 6B-Pencils = 216 × 5/9 = 120.

2. Store C: HB-Pencils sold = 400 with HB : 6B = 4 : 1, so 6B-Pencils = 400 × 1/4 = 100.

3. Store D: HB-Pencils sold = 300 with HB : 6B = 3 : 1, so 6B-Pencils = 300 × 1/3 = 100.

4. Stores C and D together therefore sold 100 + 100 = 200 6B-Pencils.

5. Required ratio = 200 : 120. Dividing both terms by their HCF, 40, gives 5 : 3.

Cross-check: scale back from each recovered value — 120 × 9/5 = 216 reproduces store A's HB figure in the table, and 100 × 4/1 = 400 reproduces store C's. As a decimal, 200 / 120 = 1.666…, which is exactly 5/3. Rows B and E carry no weight here because the question restricts the comparison to stores C, D and A.

Result: the required ratio is 5 : 3.