Basic Calculation:16

Multiplication of two numbers having digits at Ten’s places the same, but the sum of the digits at the Unit places is 10

34 × 36  = [(3×4) ×100 + (4×6)] = 1224

48 × 42  = [(4×5) ×100 + (8×2)] = 2016

53 × 57  = [(5×6) ×100 + (3×7)] = 3021

61 × 69  = [(6×7) ×100 + (1×9)] = 4209

72 × 78  = [(7×8) ×100 + (2×8)] = 5616

81 × 89  = [(8×9) ×100 + (1×9)] = 7209

43 × 47  = [(4×5) ×100 + (3×7)] = 2021

74 × 76  = [(7×8) ×100 + (4×6)] = 5624

92 × 98  = [(9×10) ×100 + (2×8)] = 9016

103 × 107  = [(10×11) ×100 + (3×7)] = 11021

Detailed Explanation: Digits at the Ten’s places are the same. One of the two equal no. is increased by one, whereas another remains the same. Then, these two numbers are multiplied. For example, in the multiplication of 34 × 36; 3 is increased by 1 and becomes 4 and the product of 3 and 4 is 12. We take 12 hundreds and the product of 4 and 6 (digits at the unit places) is 24. So, the answer is 1224.

Similarly, in the multiplication of 81 × 89; 8 is increased by one and becomes 9 and the product of 8 and 9 is 72. We take 72 hundreds and the product of 1 and 9 (digits at the unit places) is 09. So, the answer is 7209.