Some simplifications are shown below where the letter-numbers are replaced by numbers. Class 7

Some simplifications are shown below where the letter-numbers are replaced by numbers. Class 7

Question 1.

Some simplifications are shown below where the letter-numbers are replaced by numbers and the value of the expression is obtained. Class 7

1. Observe each of them and identify if there is a mistake.

2. If you think there is a mistake, try to explain what might have gone wrong.

3. Then, correct it and give the value of the expression.

Solution:

In (1), there is a mistake.

If a = -4, then 10 - a = 10 - (-4) = 10 + 4 = 14, not 6.

In (2), there is a mistake.

If d = 6, then 3d = 3 × 6 = 18, not 33.

In (3), there is a mistake.

If s = 7, then 3s- 2 = 3 × 7-2 = 21-2 = 19, not 15.

In (4), there is a mistake.

If r = 8, then 2r + 1 = 2 × 8 + 1 = 16 + 1 = 17, not 29.

In (5), there is no mistake.

In (6), there is a mistake.

If m = -6, then 3 (m + 1) = 3 (-6 + 1) = 3 × (-5) = -15, not 19.

In (7), there is a mistake.

If f = 3, g = 1, then 2f - 2g = 3 × 2 -2 × 1 = 6 - 2 = 4, not 2.

In (8), there is a mistake.

If t = 4, b - 3, then 2t + 6 = 2 × 4 + 3 = 8 + 3 = 11, not 24.

In (9), there is a mistake.

If h = 5, n = 6, then h - (3 - n) = 5 - (3 - 6) = 5 - (-3) = 5 + 3 = 8, not 4.