1到1000有多少个9

20*9+120=300
1到99共20个9 100到199
200到299 300到399 400到499 500到599 600到699 700到799 800到899
都是20个9
所以1到899
一共20*9个9
900 999 百位上的9共100个 十位上的9共10个 个位上的9共10个
一共120个9

所以1到1000共
20*9+120=300个9

一共有209个9.

9 19 29 39 49 59 69 79 89 .90.91.92.93.94.95.969.97.98.99 109 119 129 139 149 159 169 179 189.190.191.192.193.194.195.196.197.198. 199 209 219 229 239 249 259 269 279 289.290.291.292.293.294.295.296.297.298. 299 309 319 329 339 349 359 369 379 389.390.391.392.393.394.395.393.397.398. 399 409 419 429 439 449 459 469 479 489.490.491.492.493.494.495.493.497.498. 499 509 519 529 539 549 559 569 579 589.590.591.592.593.594.595.596.597.598. 599 609 619 629 639 649 659 669 679 689.690.691.692.693.694.695.696.697.698. 699 709 719 729 739 749 759 769 779 789.790.791.792.793.794.795.796.797.798. 799 809 819 829 839 849 859 869 879 889 .890.891.892.893.894.895.896.897.898. 899 900.901.902.903.904.905.906.907.908.909.910.911.912.913.914.915.916.917.918.919.920.921.922.923.924.925.926.927.928.929.930.931.932.933.934.935.936.937.938.939.940.941.942.943.944.945.946.947.948.949.950.951.952.953.954.955.956.957.958.959.960.961.962.963.964.965.966.967.968.969.970.971.972.973.974.975.976.977.978.979.980.981.982.983.984.985.986.987.988.989.990.991.992.993.994.995.996.997.998.999

300توعىز بار
--بەگارس ساۋلە وۆ

90吧

无数个（因为有小数点）