Please attempt the above question, timed and then click below to reveal the few second technique leading to the correct answer

Technique © :
Step 1. Realising that this question is on the topic of ratio, mentally allocate number one to the 3rd sibling and therefore the ratio from the 1st to 3rd sibling is

4 {2×2} : 2 {1×2} :1

Step 2. Therefore, age of the second sibling is 2/7 {1+2+4} of 42 years.=>

2/7 x 42 = 12 years

Answer: Age of the middle sibling is 12 years.

Note: Now you can mentally prove (double check) your answer is right. =>

1 x 6 + 2 x 6 + 4 x 6 = 42

WATCH OUT FOR THE VIDEO WITH IN-DEPTH EXPLANATION, ON “YOU TUBE” IN THE NEXT FORTNIGHT.

Time allowed: 30 seconds

Time taken using the technique: 3 seconds

__Time saved = 27 seconds [9/10__^{th} (90%) of time allowed by examiner]

WORK SHEET – Practice question

The total of the ages of three siblings is 36 years. The second sibling’s age is two thirds of the eldest sibling and double of the third sibling. What is the age of the middle sibling?

Step 1.=>

Step 2.=>

Answer: