Step 1: List each team's highest score across all four cups.
Sri Lanka: 280 (Cup A), 320 (Cup B), 300 (Cup C), 315 (Cup D).
India: 324 (Cup A), 285 (Cup B), 260 (Cup C), 290 (Cup D).
Step 2: Add up Sri Lanka's total.
\( 280 + 320 + 300 + 315 = 1215 \).
Step 3: Add up India's total.
\( 324 + 285 + 260 + 290 = 1159 \).
Step 4: Write the ratio of the two totals.
Sri Lanka to India is \( 1215 : 1159 \).
Checking for a common factor shows 1215 and 1159 share no simple factor, so the ratio stays as is.
Final Answer:
The ratio of Sri Lanka's total runs to India's total runs across all four cups is 1215 to 1159. \[ \boxed{1215 : 1159} \]