K-1 2. kis an even number in the series: - + - + - + ... +
1 3
:
k k k
k
2.1
2.2
2.3
Determine the number of terms in the series.
Determine the sum of the series in terms of k.
Hence, or otherwise, evaluate:
(4
(4
49
(6+2)+(+*+3)+C+
+
8
+
+
8
+
50
Go +
+ +
50 50 50
+ ... +
(5)
50​

We need to choose the nearest possible rounded off numbers for the estimation.

Step-by-step explanation:

Compatible numbers are the pairs of numbers which are easy to add, subtract, multiply, or divide mentally.

Example 1 (Addition)

600 + 300 = 900

The numbers 600 and 300 are compatible for addition, because the sum of 900 can be easily calculated mentally.

613 + 299 = 912

The numbers 613 and 299 are not compatible for addition, since the sum (912) cannot be easily calculated mentally. To estimate 613 + 299, replace 613 and 299 with the compatible numbers 600 and 300. An estimate of 613 + 299 is found by mentally calculating 600 + 300 = 900.

Example 2 (Subtraction)

20.4 − 3.8 = 16.6

The numbers 20.4 and 3.8 are not compatible for subtraction, since the difference (16.6) cannot be easily calculated mentally. To estimate 20.4 − 3.8, replace 20.4 and 3.8 with the compatible numbers 20 and 4. An estimate of 20.4 − 3.8 is found by mentally calculating 20 − 4 = 16.