Mental Maths Questions: Mental maths questions are an excellent way to enhance students calculation skills and improve their number sense. These questions require quick thinking and problem-solving abilities without the help of paper and pencil.
For example students might be asked to solve simple addition and subtraction problems such as calculating the total cost of items in a shopping list or finding the difference between two numbers. More advanced questions may involve multiplication or division, such as determining how many groups of a certain size can be made from a total. Incorporating mental maths into daily practice can boost confidence, speed and accuracy in mathematics, making it an important skill for academic success.Related Links -
Question 1: Calculate mentally:
(i) 120 + 80 + 756 + 40
(ii) 74 + 23
(iii) 57 + 89
(iv) 340 + 30 + 40
(v) 208 + 92
Solution:
(i) 120 + 80 + 756 + 40 = 996 We shall use the addition by grouping 120 + 80 = 200 50 + 40 + 6 = 96 700 + 200 + 96 = 996 (ii) 74 + 23 = 97 We shall use left-to-right addition 74 + 20 = 94 94 + 3 = 97 (iii) 57 + 89 = 146 We can use addition without carrying but it is easier to use addition with grouping (56 + 1) + 89 = 56 + 90 = 146 (iv) 340 + 30 + 40 We can use addition by grouping 40 × 2 + 30 = 80 + 30 = 110 110 + 300 = 410Read More - Math Games for Kids: Fun Ways to Learn Math
Question 2: Calculate mentally:
(i) 12 – 8
(ii) 17 – 9
(iii) 294 – 189
(iv) 34 – 27
(v) 2378 – 1876
Solution:
(i) 12 – 8 = 4 We use the trick to subtract a single-digit number from a teen number. 10 – 8 = 2 2 + 2 = 4 (ii) 17 – 9 = 8 We use the trick to subtract a single-digit number from a teen number. 10 – 9 = 1 7 + 1 = 4 (iii) 294 – 189 = 105 We shall use the technique of subtraction without borrowing 94 – 89 = 5 (Use subtraction by rounding) ∴ 234 – 189 = 105 (iv) 34 – 27 = 7 Use subtraction by rounding 34 – 30 = 4 ∵ 27 + 3 = 30 ∴ 4 + 3 = 7Question 3: Calculate mentally:
(i) 248 – 25 + 87
(ii) 305 + 45 + 23
(iii) 820 + 23 – 20
Solution:
(i) 248 – 25 + 87 = 310 Step I: 248 + 87 = 245 + 90 = 200 + (90 + 45) = 200 + 135 = 335 Step II: 335 – 25 = 310 (ii) 305 + 45 + 23 = 373 300 + (45 + 5) = 350 350 + 20 = 370 370 + 3 = 373 (iii) 820 + 23 – 20 = 823 23 – 20 = 3 820 + 3 = 823Multiplication Tricks:
Question 4: Calculate mentally:
(i) 14 × 11
(ii) 98 × 11
(iii) 47 × 11
(iv) 456 × 11
Solution:
(i) 14 × 11 = 154 Caluclate like this, 14 × 11 = 1(1+4)4. (ii) 98 × 11 = 1078 Since, 9(9+8)8 = 9(17)8 = 1078 1 of 17 is carried over to 9, 9 + 1 = 10. (iii) 47 × 11 = 517 Since, 4(4+7)7 = 4(11)7 = 517 1 of 11 is carried over to 4, 4 + 1 = 5. (iv) 456 × 11 = 5016 Just add 4560 + 456 = 5016.Question 5: Calculate mentally:
(i) 26 × 25
(ii) 35 × 17
(iii) 46 × 15
(iii) 154 × 25
Solution:
(i) 26 × 25 = 650 Half 26 and double 25, 13 × 50 Now, 13/2 = 6.5 and 6.5 × 100 = 650. (ii) 35 × 17 = 595 Half 17 and double 35, so that we get 8.5 × 70 Simply calculate 85 × 7 = (80 + 5) × 7 = 560 + 35 = 595. (iii) 46 × 15 = 690 Half 46 and double 15, so that we get 23 × 30 = 690. (iv) 154 × 25 = 3850 Half 154 and double 50, so that we get 77 × 50 Then, 77/2 × 100 = 38.5 × 100 = 3850. Few Division Tricks: Division with 2: Its easy to divide any number by 2 when its even, but it is odd, do the following: For example: 77 ÷ 2, now 77 is an odd number, Step I: take 77 – 1 = 76 Step II: half 76, 76 ÷ 2 = 38 Step III: place a .5 after 38, therefore 77 ÷ 2 = 38.5 Division by factor 10, 100, 1000, …: For example, 541 ÷ 25 Now 25 × 4 = 100 ⇒ 25 = 100/4, to find 541 ÷ 25 Step I: 541 × 4 = 2164 Step II: 2164/100 = 21.64 Similarly, to divide with 5, multiply the number by 2/10, to to divide with 125, multiply the number by 8/1000, and so on. Division by 75: Multiply the number by 4/3 then divide it by 100.Question 6: Calculate mentally:
(i) 387 ÷ 2
(ii) 8761 ÷ 2
(iii) 47 ÷ 2
(iv) 91 ÷ 2
Solution:
(i) 387 ÷ 2 = 193.5 386 ÷ 2 = 193 ∴ 387 ÷ 2 = 193.5 (ii) 8761 ÷ 2 = 4380.5 (iii) 47 ÷ 2 = 23.5 (iv) 91 ÷ 2 = 45.5Question 7: Calculate:
(i) 234 ÷ 25
(ii) 827 ÷ 5
(iii) 1356 ÷ 125
(iv) 187 ÷ 50
Solution:
(i) 234 ÷ 25 = 9.36 Step I: 234 × 4 = 936 Step II: 936/100 = 9.36 (ii) 827 ÷ 5 = 165.4 Step I: 827 × 2 = 1654 Step II: 1654/10 = 165.4 (iii) 1356 ÷ 125 = 10.848 Step I: 1356 × 8 = 10848 Step II: 10848/1000 = 10.848 (iv) 187 ÷ 50 = 3.74 Step I: 187 × 2 = 374 Step II: 374/100 = 3.74Question 8: Calculate the following:
(i) 282 ÷ 75
(ii) 45 ÷ 75
(iii) 351 ÷ 75
Solution:
(i) 281 ÷ 75 = 3.76 Step I: 282 ÷ 3 = 94 Step II: 94 × 4 = 376 Step III: 376 ÷ 100 = 3.76 (ii) 45 ÷ 75 Step I: 45 ÷ 3 = 15 Step II: 15 × 4 = 60 Step III: 60 ÷ 100 = 0.6 (iii) 351 ÷ 75 Step I: 351 ÷ 3 = 117 Step II: 117 × 4 = 468 Step III: 468 ÷ 100 = 4.68Percentages Tricks:
Question 9: Convert the following into percentages:
(i) 3.4/17 (ii) 18/50 (iii) 29/45
Solution:
(i) 3.4/17 = 20% Step I: 3.4 × 100 = 340 Step II: 340/17 = 20% (ii) 18/50 = 360% Step I: 18 × 100 = 1800 Step II: 1800/50 = 36% (iii) 29/45 = 64.44% (approx) Step I: 29 × 100 = 2900 Step II: 2900/45 = 64.44Question 10: Evaluate the following:
(i) 7% of 250 (ii) 16% of 45
Solution:
(i) 7% of 250 = 17.5 Step I: 7/10 = 0.7 and 250/10 = 25.0 Step II: 0.7 × 25 = 17.5 = 17.5 (ii) 16% of 45 = 7.2 Step I: 16/10 = 1.6 and 45/10 = 4.5 Step II: 1.6 × 4.5 = 7.2