Adapted:Learning+

Powerful Maths Methods to Solve Challenging Problem Sums 5 & 6© Singapore Asia Publishers Pte Ltd. All rights reserved.Reproducible for home/classroom use only.STRICTLY NOT FOR SALE.Look for other useful resources: www.sapgrp.com

1

Logical Reasoning

The average of three digits is 5. One of the digits is 4. What is the largest difference between the other two digits?

Solution: Total sum of three digits → 3 × 5 = 15 Sum of other two digits → 15 – 4 = 11 Largest digit possible = 9 Smallest digit of the three → 11 – 9 = 2 Largest difference between the other two digits → 9 – 2 = 7

Answer: 7

Example

1 The difference between two digits is 4. What is the largest possible sum of the two digits?

Teacher’s commentThe largest possible single-digit number is 9.

EL_Logical Reasoning.indd 1 2019/6/26 11:48:13

Adapted:Learning+

Powerful Maths Methods to Solve Challenging Problem Sums 5 & 6© Singapore Asia Publishers Pte Ltd. All rights reserved.Reproducible for home/classroom use only.STRICTLY NOT FOR SALE.Look for other useful resources: www.sapgrp.com

2

Solutions:1 To make the largest possible sum, choose the largest

pair of two digits where the difference is 4. Choosing the largest possible digit → 9 The smaller digit → 9 – 4 = 5 Largest possible sum → 5 + 9 = 14

2 Sum of 4 digits → 6 × 4 = 24 Sum of the other 2 digits → 24 – 8 – 3 = 13 Largest digit possible → 9 Smaller digit → 13 – 9 = 4 Largest difference → 9 – 4 = 5

Learn more maths methods from this book!

Primary 5&6

to Solve Problem SumsChallengingChallenging

Introduces extensive methods, concepts, thinking skills and heuristics essential for solving problem sumsTeacher’s comments to guide thinking processNon-routine questions to invoke out-of-the-box thinkingAdditional digital resources to complete learning experienceSolutions to develop the critical thinking process

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2 The average of four digits is 6. Two of the digits are 8 and 3. What is the largest difference between the other two digits?

EL_Logical Reasoning.indd 2 2019/6/27 18:16:41