IKMC 2027 - Grades 3-4 - Self-study SET 8 - Thematic Batch 3 Question 1

John has written 6, 7 and 8 in three circles, as shown. He then writes 1, 2, 3, 4 and 5 in the remaining circles so that the sum along each side is 13. What is the sum of the numbers in the grey circles?