# Question

Anyone help me with attached question

Thanks

One way to calculate the number combinations is multiply the possible choices of each order.

Order 1 is 8 or 9, therefore two choices.

Order 2, is dependent on order 1 as it cannot repeat order 1, therefore only 9 choices

Order 3 is dependent of order 1 and order 2 as it cannot repeat, therefore only 8 choices

Therefore the possible combination is the product of the three choices,

= 2 x 9 x 8 = 144 ##

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2 x 10 x 10 = 200
200 – 1 = 199 (excludes number 800)
or
801 to 999 ——- 999 – 801 + 1 = 199

808, 818, 828, 838, 848, 858, 868, 878, 888, 898 ——- 10 numbers
811, 822, 833, 844, 855, 866, 877, 899 ——- 8 numbers
880, 881, 882, 883, 884, 885, 886, 887, 889 ——- 9 numbers
909, 919, 929, 939, 949, 959, 969, 979, 989, 999 ——- 10 numbers
900, 911, 922, 933, 944, 955, 966, 977, 988 ——- 9 numbers
990, 991, 992, 993, 994, 995, 996, 997, 998 ——- 9 numbers

199 – 10 – 8 – 9 – 10 – 9 – 9  = 144

Ans : 144.

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